Hair, Fiber, and the Fabulous Phenom

Transcription

Hair, Fiber and the Fabulous Phenom: An Introduction to Forensics
Hair, Fiber, and the Fabulous Phenom
An Introduction to Forensics
for grades 6 - 12
Dorothy K. Moore, Ph.D.
Chemeketa Community College
This work was funded by the Department of Energy
2/8/10 Page 1 Hair, Fiber and the Fabulous Phenom: An Introduction to Forensics
Table of Contents
Introduction
1. Tips for Working with English Language Learners ………………………....4
2. Assessment of Prior Knowledge …………………………………………….6
3. Development of Student Vocabulary ……………………………………….9
4. Suggested Vocabulary List …………………………………………………13
5. Exploration of the Phenom ...……………………………………………….16
6. How a Scanning Electron Microscope Works ……………………………...21
7. SEM-related Handouts / Overheads Provided by the Iowa State University Materials
Science & Engineering Department
• What is the S.E.M.? ……………………................................................24
• What is an Electron Microscope? (high school level) …………………25
• What is an Electron Microscope? (elementary level) ………………….27
• How the SEM Works (high school level) ……………………………...29
• How You Can See a Sample (elementary level) ……………………….30
• Some Uses for the SEM (elementary level) ……………………………31
• The SEM Vacuum ……………………………………………………...33
• Preparing Samples / Sputter Coater …………………………………...35
8. Understanding Size and Scale ……………………………………………….39
9. Create a Reference List for Optical Microscopes…………………………….41
10. Sample Preparation for the Phenom………………………………………...45
11. Hair Analysis Part I: Discovery …………………………………………….51
12. Hair Analysis Part I Student Handout………………………………………53
13. Hair Analysis Part II: Lecture……………………………………………….55
14. Hair Analysis Part II Background Notes.……………………………………59
15. “I-Search” Research Activity ………………………………………………..65
16. Hair Analysis Part III: Analyze and Identify Unknown Samples of Hair...…70
17. Comparing Evidence Student Handout……………………………………...72
18. Forensic Fiber Examination Background Information...…………………….74
19. Calculate the Medullary Index……………………………………………….79
20. Identify Weave Patterns………………………………………………………82
21. Observe and Describe the Features of Fiber………………………………….87
22. Distinguish Between Natural vs. Synthetic Fiber…………………………….90
23. Fiber Analysis Background Information……………………………………..93
24.Trace Evidence and the Significance of Fiber………………………………...96
25. Locard’s Exchange Principle………………………………………………..100
26. Probability…………………………………………………………………...105
27. Writing Clear Lab Reports...………………………………………………...108
28. The CSI Effect...…………………………………………………………….112
29. Closure…...………………………………………………………………….114
30. Visuals…...…………………………………………………………………..116
31. References …………………………………………………………………..122
Hair, Fiber, and the Fabulous Phenom: An Introduction to Forensics
Teaching adolescents is not for the weak or faint-hearted. Twenty-first century students
are more knowledgeable and technologically adept than any generation before them.
Even the cell phones they carry today can link them instantaneously to all forms of
information, entertainment, and social networking. It goes without saying then, that
today’s youth present teachers with a tremendous challenge to stay current, relevant, and
strong.
To that end I have written Hair, Fiber, and the Fabulous Phenom: An Introduction to
Forensics. With the current interest in forensic science on the rise (thanks to some
popular television shows), teachers with access to the Phenom scanning electron
microscope have the unique opportunity to combine the intrigues of forensics with
cutting edge technology. As teachers know, when the right tool is coupled with a
challenging topic, students are far more inclined to stay focused on what they are
learning. I believe that coupling forensic fiber analysis with a real SEM is a sure way to
capture and sustain the imagination of even the most technologically savvy teenager.
Hair, Fiber, and the Fabulous Phenom: An Introduction to Forensics is a standardsbased integrated unit appropriate for grades 6-12. Designed to introduce students to the
language, methods, and tools of the forensic scientist, this unit combines math and
literacy with the thinking and observational skills used by forensic scientists. Adapted
from lessons developed by other practicing teachers, the activities presented here are
appropriate for a wide range of age and developmental abilities. In addition, many of the
activities can be easily modified or extended, depending on the availability of time,
materials, or your students’ needs. And for those of you who wish to learn more, I have
included additional websites and resources at the end of each lesson to get you started in
your search.
To the question, “Does it matter the order in which the lessons are taught?”, the answer is
both yes and no. For the most part, the lessons are ordered so that one lesson leads
logically into the next. There are a number of exceptions, though. For example, “Tips for
Working with English Language Learners” and “Developing Student Vocabulary” will
work anywhere throughout the unit. The “I-Search Activity,” “Calculate the Medullary
Index,” and “Probability” will also work anywhere that fits into your curriculum. And as
indicated earlier, how you choose to modify or adapt these activities is entirely up to you:
No one knows students, their interests, or their needs better than those of you who work
with them on a daily basis.
One last word about the Phenom itself: As a former 6th-grade teacher with no formal
training in electron microscopy, I can identify with those of you who might feel
somewhat intimidated by such a sophisticated classroom tool. For many of us, figuring
out the tool bar on the computer screen is just about all the technology we can handle.
But let me assure you that with just a little amount of time and practice, the Phenom
becomes really quite easy and fun to explore. Moreover, it’s the kind of tool that will
engage students, freshen the curriculum, and help keep you strong.
1. TIPS FOR WORKING WITH SECOND LANGUAGE LEARNERS
National Science Teaching Standard B: Teachers of science guide and facilitate
learning. In doing this, teachers recognize and respond to student diversity and encourage
all students to participate fully in science learning.
Suggestions for making your language more understandable and accessible to
second language learners:
1) Use plenty of objects, videos, and pictures within the context of
teaching and lab
work. Refer to diagrams and photos whenever possible, and allow students to
process in pairs and small groups what they see in videos and YouTube clips.
2) Teach and develop key vocabulary within the context of the lab activities. For
example, while the second language learner operates the Phenom, the teacher or
peer can be pointing out key items or procedures.
3) Offer periodic summaries and paraphrases. Allowing students to summarize key
ideas in small groups gives second language learners the opportunity to seek the
clarification they need on an individual basis.
4) Include first language support wherever possible.
For example, when students are
exploring Phenom images or writing summaries of what they are learning, allow
them to communicate in their first language. Students with strong skills in their
first language make greater academic progress in the second language as well.
5) To help students understand written text, teach a variety of reading
comprehension strategies. Show your second language learners how to ask
questions about the visuals, titles, and subheadings before they read the text.
Teach them to read the first sentence of each paragraph to learn what the longer
selection is about. Also explain to students how reading the concluding
paragraphs first provides key ideas in just a few sentences. You might also let
some students summarize the main ideas of the text in their first language after
listening to a peer read the text to them.
6) Above all, allow your students the freedom to make mistakes. When being wrong
is recognized as a natural step in learning a new language (be it English or
microscopy), students will progress more quickly towards getting it right.
For more information on working with second language learners
Cary, S. (2000). Working with Second Language Learners: Answers to Teachers’ Top
Ten Questions. Portsmouth, NH: Heinemann.
Larsen-Freeman, D. (2008). Techniques and principles in language teaching (2nd ed.).
Oxford University Press.
2. ASSESSMENT of PRIOR KNOWLEDGE
Objective
Students reveal what they already know about hair, fiber, and forensic science.
National Science Teaching Standard A: Teachers of science plan an inquiry-based
science program for their students. In doing this, teachers select science content and adapt
and design curricula to meet the interests, knowledge, understanding, abilities, and
experiences of students.
Rationale
Students are more interested and motivated to learn when content is developed around
their own experience and prior knowledge. In this KWL activity students share what they
already know --- and want to know --- about the topic of hair, fiber and forensic science.
Materials
Butcher or chart paper
Hook and Focus
Teacher: “Think for a minute, of all the people so far today that you either touched, or
who brushed up against you, or whose jacket or backpack you might have come in
contact with, even if it was accidental. (Allow enough “think time” for the students to
focus and respond to your question.)
“Now look at your clothing: Do you see any apparent evidential hairs or fibers that might
support your claim that were you in contact with those people? (Allow a brief discussion.
The students should realize that for most encounters evidentiary hairs and fibers are not
immediately apparent.)
“What if we needed scientific proof – not circumstantial evidence – but real scientific,
empirical proof that you were with that person today? How could we prove that you were
near that person today even when we can see absolutely nothing that indicates you were
even near that person? As you might know from television, there are scientific
procedures for determining the probability that you were in contact with others today…
And for the next few weeks we will study and learn the procedure and thinking processes
of forensic hair and fiber examiners.
“Many of you already know perhaps from television or from reading, something about
how forensic scientists operate – the things they do, the things they think about, the ways
they talk. So we’ll start with what you already know. Understanding what you already
know about this topic will help me prepare the learning activities we do in the days
ahead.”
Procedure:
1. The teacher guides the students in the creation of a KWL chart:
a. In small groups students brainstorm and record in their science journals what
they already think they know about the topic hair, fiber, and forensic scientists, scientists
who collect and analyze evidence, including evidence that cannot be seen with the naked
eye.
b. The class returns as a whole group, sharing the results of their small-group
discussion while the teacher records their contributions on large butcher paper. The
butcher paper is labeled “What we think we Know about hair, fiber, and forensic
scientists.”
c. After all ideas have been shared, the teacher asks the students what they would
like to learn during the unit related to forensic scientists. S/he records their questions on a
new sheet of butcher paper labeled “What we Want to learn.” Students also record their
questions in their science journals.
Closure
Teacher: “In the days ahead we will seek to answer the questions you have posed
regarding hair, fiber, and forensic scientists. Also in our studies we will seek to confirm
or alter what we think we already know about hair, fiber, and forensic scientists. And in
the process of learning about hair, fiber, and forensic science, we will develop and
sharpen the thinking skills we need to help determine the answer to our initial question:
How can we ‘prove’ – using hair and fiber analysis – that you were in contact with
another, especially when there appears to be no visible proof?
For more information on the KWL strategy
http://olc.spsd.sk.ca/DE/PD/instr/strats/kwl/
brief explanation of the KWL strategy
http://www.indiana.edu/~l517/KWL.htm
clear explanation of purpose and procedure for the KWL. Includes example
https://www.msu.edu/course/cep/886/Reading%20Comprehension/7Learn_Serv_Proj_K
WL.html
very simple outline of the KWL strategy applied to reading
For more information on forensic science
http://www.youtube.com/watch?v=ekTbRJbN6is
quick overview of forensic scientists
http://www.all-about-forensic-science.com/
lots of information
http://www.aafs.org/yfsf/index.htm
young forensic science forum
http://wiki.nsdl.org/index.php/MiddleSchoolPortal/Forensic_Science
justification for teaching forensic science in middle school
http://www.phenomworld.com/applications/education.php#http://hwcdn.net/b3d9w2e7/cds/phenom/FEI_NC
SU_Classroom_Instruction_F8_Medium.flv
video showing the value of using the Phenom in hair and fiber analysis
Forensic science resources for the beginner
Cooper, C. (2008). Eyewitness: Forensic science. London: DK Publishing.
Pentland, P., & Stoyles, P. (2003). Science and Scientists: Forensic Science. Broomall,
PA: Chelsea House Publishers.
Rainis, K.G. (2006). Hair, clothing, and tire track evidence: Crime-solving science
experiments. Berkeley Heights, NJ: Enslow Publishers, Inc.
Sheely, R. (1993). Police lab: Using science to solve crimes. New York: Silver Moon
Press.
Yeatts, T. (2001). Forensics: Solving the crime. Minneapolis: The Oliver Press, Inc.
Yount, L. (2007). Forensic science: From fibers to fingerprints. New York: Chelsea
House Publishers.
3. DEVELOPMENT OF STUDENT VOCABULARY
Objective
Students develop conceptual understanding of important terminology by drawing on prior
knowledge and personal experience.
National Science Content Standard A: Communicate scientific procedures and
explanations.
Rationale
The expression and understanding of any idea is dependent upon one’s word knowledge.
Moreover, an individual’s reading comprehension is significantly affected by her/his
vocabulary development. Pre-teaching and developing key vocabulary is an effective way
to scaffold students’ conceptual understanding of the world. Below are three different
strategies for preparing students’ conceptual understanding of key terminology
encountered throughout this unit of study.
Strategy #1: The 10 Most Important Words
1. Ask students to individually list what they predict to be the ten most important
words or phrases they will encounter in the upcoming unit or reading selection.
2. Students compare their lists in small groups, discussing the reasons for selecting
the words they did.
3. Each small group develops a new list of the ten most important words they predict
will be in the upcoming unit or reading selection.
4. Students then read the pertinent reading selection (or begin the new unit of study),
paying close attention to key concepts.
5. After reading the material, each group revises their original list, providing written
rationales for the words they have selected for their final list.
Strategy #2: Vocabulary Alert!
1. The teacher selects between 5-9 key terms from the reading selection or unit of
study, issuing a handout with a 1-9 familiarity scale for each term.
2. Students use the scale to assess their prior understanding of each new vocabulary
word.
3. The teacher explains the significance of each term within the context of the topic,
and prepares the students for reading or instruction.
4. As the students read, they record information about the term on the given form.
5. After reading the selection, the class engages in a discussion of the new
terminology in order to clarify and further develop understanding of the terms.
Term:_______________________
Don’t know
It’s sort of familiar
1
2
3
4
5
6
7
I know
8
9
Term:_______________________
Don’t know
1
2
3
4
5
6
7
I know
8
9
7
I know
8
9
Term:_______________________
Don’t know
1
2
3
4
5
6
Strategy #3: 4-Square Vocabulary Approach
Note: Once students become familiar with this strategy, they can use it independently
throughout the unit.
1. Students divide paper into 4 squares.
2. In Square 1 students write the key term. The teacher explains the term in context,
provides the definition, and provides examples and non-examples of the term.
3. In square 2 each student writes (and possibly illustrates) an example from
personal experience that fits the term.
4. In Square 3 each student writes (and possibly illustrates) a non-example of the
term
5. In Square 4, each student writes a definition of the term using her/his own words.
6. The class discusses the term once more, and the students refine their definitions, if
necessary. They then locate the term in the context of the reading or unit material.
Example from Social Studies
(square 1)
compromise
compromised
compromising
(square 2)
Sometimes people have to settle things by
giving up something they want.
Some government delegates had to agree to
give up some things they wanted to reach an
agreement
(square 3)
(square 3)
The fighting couple could not settle A compromise is an agreement between two or
their differences and so they divorced.
more people or groups where both must give
An agreement between the two up something.
countries was not reached, and so a war
was started.
Source: Stephens, E.C. & Brown, J.E. (2000). A handbook of content literacy strategies:
75 practical reading and writing ideas. Norwood, MA: Christopher-Gordon Publishers,
Inc.
Assessment
In their science journals, the students write in response to one of the following prompts.
These prompts are based upon Howard Gardner’s Theory of Multiple Intelligences:
a. Using five of the vocabulary terms learned in class this week, write two or three
paragraphs describing your understanding of ______ (Locard’s Exchange
Principle, for example).
b. Create a visual illustration related to our discussion of this week’s vocabulary
terms. Label your illustration using five of the terms above.
c. Create a 4-pane comic strip using five of the terms discussed in class this week.
d. Create an acrostic poem out of one of the vocabulary terms discussed in class this
week. Within your acrostic, include four addition vocabulary terms.
e. Prepare a brief dramatization to present to your study group. Embed within the
monologue five of the vocabulary terms learned this week.
For more information on vocabulary strategies
Stephens, E.C. & Brown, J.E. (2000). A handbook of content literacy strategies: 75
practical reading and writing ideas. Norwood, MA: Christopher-Gordon Publishers, Inc.
This is the source of the three strategies included.
4. SUGGESTED VOCABULARY LIST BY CATEGORY
Hair, Fiber, and the Fabulous Phenom: An Introduction to Forensics
MICROSCOPY
microscopical
optical microscope
scanning electron microscope
stereomicroscope
comparison microscope
compound light microscope
scanning electron microscope
polarized light microscope
polarized light
photomicrograph
sputter coat
backscatter electrons
field of view
morphology
THE PHENOM
optical imaging position
electron imaging position
optical camera
main viewing window
image screen
button bars
image setting
data bar
dynamic representation
current ruler size
magnification factor
field of view
rotary knob
loading position
resolution
electron beam setting
HAIR
ovoid bodies
distal
pigment granule
cortical fusi
cuticle
cortex
medulla
medullary index
coronal scales
FIBER
degree of rarity
textile
weave pattern
plain
twill
satin
uncut pile
cut pile
felt
crimp
relative diameter
luster
lumen
apparent cross section
adhering debris
dislocations
thickness
dyes
synthetic
rayon
acetates
acrylic
delustrant particles
inorganic fiber
manufactured fiber
natural fiber
synthetic fiber
technical fiber
thermoplastic fiber
FORENSIC SCIENCE
Trace evidence
CSI Effect
Locard’s Principle
probative value
evidentiary
known sample
questioned sample
class characteristics
individual characteristics
primary transfer
secondary transfer
5. EXPLORATION OF THE PHENOM
Objective: Students discover the purposes and capabilities of the icons displayed on the
Phenom’s interactive touch screen interface.
National Science Content Standard E: Understandings about science and technology:
Science and technology are reciprocal.
Rationale: The Phenom, especially designed for student use, allows students to navigate
samples by using the tool’s touch screen interface. As students explore the features of the
table top scanning electron microscope (TT-SEM), they gain confidence in their ability to
conduct scientific investigations.
Hook and Focus
Teacher: “In the days ahead you will be analyzing hair and fiber similar to the ways
forensic scientists analyze them. Many times you’ll be working with the Phenom
scanning electron microscope in small groups while the rest of the class is working on
other assignments. Therefore, you’ll need to be totally confident and proficient in using
the Phenom independent of my help.
Later you’ll learn how the SEM works on the inside, but today you’ll be learning on your
own how to operate this imaging tool so that you won’t be hindered by the technology in
your later scientific investigations.”
Procedure
Before class the teacher pre-loads into the Phenom a prepared sample stub of an
insect (See the Technical Manual for directions).
1. The teacher demonstrates and explains that after closing the Phenom door, the
sample automatically transfers to the optical imaging position.
2. The optical camera becomes activated and the image is displayed in the main
viewing window of the image screen.
3. S/he shows how part of the sample is displayed in both the main viewing window
and the optical overview window, and explains that each group will be exploring
the button bars in the Image Setting to learn how to do everything from
adjusting the focus and brightness to taking pictures of the image.
4. To capture the image in its entirety, the teacher touches the “composite image
overview” icon, explaining that the mechanical noise they hear is the sample
holder moving into nine different positions so as to capture the image from each
position.
5. Once the image is completely displayed, the teacher explains that each small
group will be given a list of functions the Phenom is capable of performing. The
students’ task is to draw a picture of the icon that activates each of the given
functions. Students work in small groups of 3 or 4. The teacher can model the
process by illustrating the “composite image overview” icon s/he just activated.
For more student-friendly information on the Phenom in general
http://www.youtube.com/watch?v=n3Xngnnv47w&NR=1
YouTube: Youngsters using the Phenom
http://www.youtube.com/watch?v=YfHkpM7gXjk&NR=1
YouTube: Phenom featured on CSI NY
http://www.youtube.com/watch?v=Rk7jGgMlPek&feature=related
YouTube: FEI promo of the Phenom
http://www.phenomworld.com/applications/education.php#http://hwcdn.net/b3d9w2e7/cds/phenom/FEI_Hea
lth_and_Science_School_Fl8Medium.flv
high school students describe the value of the Phenom SEM
THE FABULOUS PHENOM: AN EXPLORATION
Directions: Draw the icons that allow you to perform the functions described. Your
group has 30 minutes. If you need help, press the ? and the information balloon will
help you.
Æ
All answers are found in the Image Screen setting. Please stay within the
boundaries of the Image Screen. Å
1. Look below the main viewing window to view the data bar. You will see a
dynamic representation of the current ruler size of the sample you are looking
at. It will look like something like this:
I_____I_____I_____I_____I_____I_____I What is the current ruler size of the
sample you are viewing?
2. Look just to the right of the ruler. The top symbol shows the current
magnification factor of your sample. Draw the icon that represents the
magnification factor.
3. Just below the magnification factor is a symbol showing the total picture size you
are looking at. This is also known as the Field of View. Draw the Field of View
symbol.
4. What is the current date and time?
5. What is the file name of this sample? (It’s listed below the date and time.)
6. See the lower right hand corner of the button bar. Each button is associated with
a different function of the blue-lighted rotary knob. Draw the icon that does the
following:
a. Magnifies part of the image when it is in the electron imaging mode.
b. Adjusts the contrast of the image.
c. Adjusts the brightness of the image.
d. Adjusts the focus of the image.
e. Rotates the image when it is in the electron imaging mode.
7. Use the rotary knob to adjust the focus and brightness of the optical image. Try
to adjust the “fine focus” of the image using both the rotary knob and the focus
icon. Which method does your group prefer to use? Why?
Draw the icon associated with the following functions:
8. This icon allows you to take a picture of the image when it’s in the electron
overview window.
9. You might have noticed that if the sample moves outside of the original field of
view, the electron overview window will turn black. To refresh the electron
overview window, touch the refresh icon. Draw a picture of that icon here.
10. This icon allows you to take a picture of the image when it’s in the optical
overview window.
11. See the top right hand corner of the button bar. Draw the icon for each of the
functions listed below.
a. Transfers the sample from its loading position to the optical imaging
position and back again.
b. Allows the user to select between electron imaging or optical imaging.
Describe how you know which mode is active.
c. This icon allows you to take a digital picture of the image in the main
viewing window.
12. How do you move the sample up, down, left or right? Draw the icon.
13. To increase the resolution of your image, change the Phenom from the optical
setting to the electron beam setting. First center the part of the image you want
to view in the optical overview window. Then touch the “electron imaging” icon
to select the electron imaging position.
14. The focus can be set to either automatic or manual control. How do you change
between automatic and manual control? (Use the information balloon if you
need help.)
6. HOW A SCANNING ELECTRON MICROSCOPE WORKS
Objective
Students compare and contrast optical microscopy with electron microscopy.
National Science Content Standard E: Understandings about Science and Technology
National Science Content Standard B: Transfer of Energy
Rationale
A common misconception among adolescents is that science influences technology, when
in actuality technology is more apt to influence science. In this lesson students learn how
the SEM works technologically, but they also consider ways the tool has changed
science, forensics, and the world in which we live.
Materials
Written material (attached)
Hook and Focus
Teacher: “As you saw when working with the Phenom, the scanning electron microscope
allows you to see images at a much greater magnitude and resolution than that of the
optical microscope. But why is that? How does the Phenom or other scanning electron
microscopes work? As we consider the features and mechanisms of the scanning electron
microscope, be thinking about how the technology associated with the SEM has
influenced forensics and other areas of our world.
Procedure
The attached information has been reproduced with permission from the Iowa State
University Materials Science and Engineering Department. Depending on the needs of
the classroom, teachers may reproduce the contents as handouts or provide the
information in lecture form. Two versions are given, one for less experienced science
students and readers, and one for more experienced or older science students and readers.
Assessment ideas
Students can summarize how a SEM works by creating a simplified, age-appropriate
version for students in a younger grade.
Students might debate, discuss, or write papers on how the technology used in the SEM
has influenced other areas of science.
For more information on the scanning electron microscope
http://www.fei.com/resources/web-resources-links.aspx
FEI website
http://www.fei.com/uploadedFiles/Documents/Content/2006_06_AllYouWanted_pb.pdf
produced by FEI; includes dynamic visuals
http://www.mse.iastate.edu/microscopy/home.html
includes age-appropriate descriptions and diagrams of the SEM for elementary, high
school, and college level students. The attached handouts come from this site.
http://school.discoveryeducation.com/lessonplans/activities/electronmicroscope/
includes ‘how a SEM works’ within the body of the procedure
http://www.jsu.edu/depart/biology/learning_about_microscopy.html#thelightmicro
includes a paragraph which sums up how a SEM works. Appropriate for more
experienced readers.
http://www.coe.uh.edu/archive/science/science_graphics/sciencegr2.html
compound microscope
http://www.unl.edu/CMRAcfem/semout.htm
SEM images
http://micro.magnet.fsu.edu/primer/index.html
good for learning the vocabulary in context for microscopy
http://www.youtube.com/watch?v=fToTFjwUc5M
YouTube: The structure and function of the scanning electron microscope
http://www.lessonplanet.com/directory/Science/Biology/Microscopes/Scanning_Electron
_Microscopes
lesson plans for scanning electron microscopes
http://www.5min.com/Video/Scanning-and-Transmission-Electron-Microscopes150625001
five minute, clear explanation of SEMs and STEMs.
For more information on forensics and the scanning electron microscope
http://www.enotes.com/forensic-science/scanning-electron-microscopy
SEM and forensics
http://www.enotes.com/forensic-science/microscopes
SEM and forensics
http://www.enotes.com/forensic-science/inorganic-compounds
SEM and forensics
http://www.enotes.com/forensic-science/search?m=cs&url=forensic-science&q=SEM
includes a bit on how the SEM is used with forensics
WHAT IS THE S.E.M.?
This is the
SEM in the
Iowa State
MSE Department
The Scanning Electron Microscope (SEM) is a microscope
that uses electrons rather than light to form an image. There
are many advantages to using the SEM instead of a light
microscope.
The SEM has a large depth of field, which allows a large
amount of the sample to be in focus at one time. The SEM
also produces images of high resolution, which means that
closely spaced features can be examined at a high
magnification. Preparation of the samples is relatively easy
since most SEMs only require the sample to be conductive.
The combination of higher magnification, larger depth of
focus, greater resolution, and ease of sample observation
makes the SEM one of the most heavily used instruments in
research areas today.
Used by permission
http://www.mse.iastate.edu/microscopy/whatsem.html
What is an Electron
Microscope?
The development of the Scanning
Electron Microscope in the early
1950's brought with it new areas
of study in the medical and
physical sciences because it
allowed examination of a great
variety of specimens.
As in any microscope the main
objective is for magnification and
focus for clarity. An optical
microscope uses lenses to bend the
light waves and the lenses are
adjusted for focus. In the SEM,
electromagnets are used to bend
The first modern scanning electron
an electron beam which is used to
microscope,
produce the image on a screen. By
constructed by D. McMullan in the
using electromagnets an observer
Cambridge
University Engineering Laboratory in 1951.
can have more control in how
Source: Electron Optics and Electron Microscopy,
much magnification he/she
P.W. Hawkes.
obtains. The electron beam also
provides greater clarity in the
image produced.
A modern version of the SEM.
The SEM is designed for
direct studying of the
surfaces of solid objects. By
scanning with an electron
beam that has been
generated and focused by
the operation of the
microscope, an image is
formed in much the same
way as a TV. The SEM
allows a greater depth of
focus than the optical
microscope. For this reason
the SEM can produce an
image that is a good
representation of the threedimensional sample.
Used by permission
http://www.mse.iastate.edu/microscopy/highschool.html
What is an Electron
Microscope?
A microscope is very similar to a telescope
or, for that matter, a pair of eye glasses. All
microscopes, telescopes, and glasses have
something in common - lenses. A lens is
usually made out of glass and it takes light
and bends it so that we can see things more
clearly. In glasses, the lenses will bend the
light so that things that appear "fuzzy" are
brought into focus. In telescopes, lenses
take things that are far away and make
them appear as if they are close to us so we
can see them better. In microscopes, lenses
take things that are very small and magnify
them so they become visible.
Light microscopes are used in a number of areas
such as medicine, science, and engineering.
However, light microscopes can not give us the
high magnifications needed to see the tiniest
objects like atoms. For this, we have to use
electrons rather than light. Electrons are small
particles within the atom. Microscopes that use
electrons rather than light are called electron
microscopes.
Since we are not using light in
electron microscopes, we can not use
glass for our lenses. Instead we use
magnets. Magnets will make electrons
bend just as glass makes light bend.
These magnets let us magnify images
and bring them into focus. Since you
can't really see electrons with your
eyes we have to use some other
equipment to produce a television
signal that shows an image on a TV
screen. Your TV at home uses
electrons to produce an image, too. A
scanning electron microscope really is
a big fancy TV attached to some
magnets!
Used by permission
http://www.mse.iastate.edu/microscopy/elementary.html
How the SEM Works
The SEM uses electrons
instead of light to form
an image. A beam of
electrons is produced at
the top of the
microscope by heating
of a metallic filament.
The electron beam
follows a vertical path
through the column of
the microscope. It
makes its way through
electromagnetic lenses
which focus and direct
the beam down towards
the sample. Once it hits
the sample, other
electrons (
backscattered or
secondary ) are ejected
from the sample.
Detectors collect the
secondary or
backscattered electrons,
and convert them to a
signal that is sent to a
viewing screen similiar
to the one in an
ordinary television,
producing an image.
Used by permission
http://www.mse.iastate.edu/microscopy/path2.html
How You Can See a Sample
Electron microscopes use something similar to a light bulb
to produce electrons. This is called the filament. The
filament is a piece of wire and when electricity goes
through it, not only is light given off, but also electrons.
These electrons are focused by a series of magnets. The
magnets are made magnetic by electricity and are called
electromagnets. The electrons can be focused on the sample
and when they hit the sample a signal is given off. A
special type of detector acts like a TV camera and the
image of the sample is displayed on a TV screen. By
changing how the electrons are bent and how the beam of
electrons strikes the sample, you can change the
magnification and focus of the TV image.
Used by permission
http://www.mse.iastate.edu/microscopy/look.html
Some Uses for the SEM
Medical Uses
A medical researcher can use a SEM to
compare samples of healthy and
unhealthy blood and tissue samples to
determine what is causing an illness in a
patient. They can also study the effect of
medicine on a patient by observing the
differences between the unhealthy
patients and those patients given
medicine.
Forensics
Police laboratories need SEM's to
examine evidence. A SEM can be used to
compare such things as metal fragments,
paint, and inks. Hair and fibers can also
be examined to prove a person's guilt or
innocence. By comparing a sample found
at the scene of a crime to a similar sample
found belonging to a suspected criminal,
detectives can closely determine if the
samples are a match.
Metals
Metal samples can be examined with the
SEM to determine strength in different
conditions such as cold and heat. Experts
study the metal from the frame of a crashed
airplane to determine if there was a flaw in
the metal that caused the crash. Studies are
also done on the metal before it is used in a
plane, car, train, boat or anything that would
require a strong metal for reasons of safety.
By studying samples from the hull of the
Titanic, scientists were able to discover that
the metal had shattered because the cold
water had caused it to become brittle.
Scientific Research
There are many different areas in scientific
research where the SEM can be used. Any scientist
that needs to look at extremely small samples can
use the SEM. For example, Biologists use the SEM
to look at plant or animal cells and tissues,
Chemists examine microscopic crystals, and
Material Scientists view the structure of metals,
ceramics, and plastics. These are only a few of the
ways a SEM can be used for scientific research.
[
The SEM Vacuum
When a SEM is used, the column and sample must always
be at vacuum. A vacuum environment means that most of
the air molecules have been removed from the inside of the
microscope. You can think of vacuum as a density; there
are a certain number of gas molecules in a given space. If
you think of the total number of people in the United States
(240 million) as representing normal atmospheric pressure,
then the density of gas molecules in a typical SEM is
roughly equivalent to having only one person inhabit the
entire United States!
There are many reasons for requiring a vacuum in an SEM.
If the filament were surrounded by air, it would quickly
burn out, like a light bulb. If the column were full of air, the
electrons would collide with the gas molecules and never
reach the sample. If gas molecules react with the sample
different compounds could form and condense on the
sample. This can lower the quality of the image.
A vacuum environment is also necessary in part of the
sample preparation. One such example is the sputter coater.
Used by permission
http://www.mse.iastate.edu/microscopy/vacuum2.html
Preparing Samples
Since the SEM uses electrons to produce an image, most
conventional SEMs require that the samples be electrically
conductive. Specially designed SEMs called environmental
SEMs are now available which can be used to view nonconductive or even wet samples. The regular SEM, which
we have in the Iowa State Materials Science Department,
requires a conductive sample. All metals are conductive
and require no preparation to be viewed using an SEM. In
order to view non-conductive samples such as ceramics or
plastics, we must cover the sample with a thin layer of a
conductive material. We do this using a small device called
a sputter coater.
Sputter Coater
A sputter coater coats the sample
with gold atoms. The purpose is to
make non-metallic samples
electrically conductive.
The sputter coater uses argon gas and a small electric field.
The sample is placed in a small chamber which is at
vacuum. Argon gas is then introduced and an electric field
is used to cause an electron to be removed from the argon
atoms to make the atoms ions with a positive charge. The
Ar ions are then attracted to a negatively charged piece of
gold foil. The Ar ions act like sand in a sandblaster,
knocking gold atoms from the surface of the foil. These
gold atoms now settle onto the surface of the sample,
producing a gold coating.
Used by permission
http://www.mse.iastate.edu/microscopy/prep2.html
8. UNDERSTANDING SIZE AND SCALE
Objective
Students use Greek and Latin roots to identify the size and scale of images at
the microscopic level.
National Science Program Standard C: The science program should be
coordinated with the mathematics program to enhance student understanding
of mathematics in the study of science and to improve student understanding
of mathematics.
Rationale
Gail Jones, author of Nanoscale Science, explains how important it is that
students understand scale: “Scale is one of the big ideas that cross the
science domains...scale is an essential tool to understand the universe in a
scientific way.” In this lesson, students apply their understanding of Greek
and Latin roots to help them comprehend scale.
Materials
Meter stick
Dictionary
Hook and Focus
Display meter stick and read from the dictionary the definition of meter:
“The basic metric unit of linear measure, equal to c. 39.37 inches.” Remind
students that the metric system is a decimal system that uses the meter as the
basic unit of length.
Teacher: “What other metrical terms of measure are you familiar with?
(Allow for a few contributions. Students might offer terms such kilometer,
milliliter, kilogram. Accept all responses, but do not explain or define any of
the terms at this point.)
“These are all units of measure, some of which we are more familiar.
However, when talking about things at the microscopic level, it can be
confusing trying to understand just how big or small something is --- unless
we understand exactly what the mathematical term means.
“By using this meter stick as our standard unit of measure, we can determine
the meaning of a particular unit of measure once we know what the root
word means.”
Procedure:
1. Display as a wall chart or provide handouts of the following
information:
meter < Greek metron, meaning to mark off, to measure.
1 meter = (m)
decimeter = 1/10th meter (dm)
centimeter = 1/100th meter (cm)
milliliter = 1/1000th meter (mm)
micrometer = 1/1,000,000th meter (µn)
(micrometer = micron, but micron is an obsolete term)
(millimicron = 1/1000th micron; millimicron = 1/1,000,000,000 meter,
but
millimicron is an obsolete term.)
millimicron = nanometer (nm)
nanometer = 1/1,000,000,000th meter (nm)
nm = mµ
1 nm = ten Angstroms
2. In small groups, students generate lists of other words they know for
each root: deci- centi- milli- micro- nano3. Once each group has exhausted known words with the given roots,
students predict the meaning of each root.
4. Students check their list and predicted definition against the
dictionary.
5. Students sketch what they believe _____ [insect eye; finger nail,
penny; pollen; etc.] will look like at various magnifications.
6. Using images from the Phenom, students sketch what the [insect eye;
finger nail; penny; pollen; etc.] looks like at the various levels of
magnification.
Optional Extensions
• YouTube offers a few informative, entertaining clips that help the
viewer understand size at the nanoscale. After viewing one or two of
these, let students devise their own analogy.
http://www.youtube.com/watch?v=OxlAUFqIiqA&feature=related
http://www.youtube.com/watch?v=qrUzfUcMtaA&NR=1
• A meter is equal to the distance light travels in a vacuum in
1/299,793,458 of a second. Ask students to calculate how many
nanometers this is.
For more information on size and scale
http://www.youtube.com/watch?v=FXZwi7Lf9Yw&feature=channel
explains how small a nanometer is. Quick video.
http://www.youtube.com/watch?v=1Nl87_pqOZ4&feature=related
brief. gives analogies for the size of a nanometer
http://www.magnetmail.net/Actions/email_web_version.cfm?publish=newsletter&user_i
d=NSTA&message_id=627591
magnitude and scale links for elementary level students. NSTA
http://www.nisenet.org/viz_lab_image_scaler
image scaler from human to nano
http://www.youtube.com/watch?v=8BTGzVScBso&feature=channel_page
Entertaining introduction to nanotechnology, produced by OMSI
Rob Sleezer has developed middle school lessons that teach size and scale using the
Phenom SEM. He is at the University of Arkansas. rzleezer@uark.edu
For information related to nanotechnology
http://science.howstuffworks.com/nanotechnology.htm
good visuals – related to nanotechnology
from FEI’s website. This links to several related websites for nanotechnology
http://www.youtube.com/watch?v=Cm90Md81zZQ&NR=1
Intro to nanotechnology. Narrated by Alan Alda.
http://www.youtube.com/watch?v=gYR8lV23Pow&feature=fvw
Nanotechnology. 9 minutes
http://www.youtube.com/watch?v=S4CjZ-OkGDs
10 ½ minutes explaining nanotechnology
http://www.nisenet.org/
links to sites and information on nanotechnology
9. CREATE A REFERENCE LIST FOR OPTICAL MICROSCOPES
[See “Sample Preparation for the Phenom SEM” for directions on preparing permanent
sample stubs for use with the table top scanning electron microscope.]
Objective
Students develop a reference collection of known hair and fiber samples (K) for use with
optical microscopes.
National Science Content Standard F: Science and Technology in Society
Rationale
When content is presented within the context of authentic activity, students are able to
construct a deeper, more integrated understanding of the knowledge and skills presented
to them. Students are also able to see the relevance of what they learn in school when
engaged in activities they know to be useful beyond the classroom walls. The reference
list that is developed by the students throughout this forensic unit resembles the one
forensic scientists refer to when comparing known evidence (K) against the evidence that
is in question (Q).
Note to teacher: In this activity students develop a reference collection of known
samples (K) of hair and fiber to compare against samples in question (Q). Once this
reference collection is substantial in size, students can bring in further samples for
testing, comparing the unknown hairs and fibers (Q) with those from the reference list
(K) they have developed.
Materials (students contribute)
Paper bags
Tweezers
Paper envelopes
Permanent black ink markers
Clear sticky tape
Unlined index cards
Animal hair samples
Human hair samples
Fabric samples: polyester, cotton, linen, wool
Plant samples: linen, cotton, hemp
Magnifying glasses
Desk lamp
Light corn syrup
Paper cup
Microscope slides
Medicine dropper
Plastic cover slips
Compound microscope 400+ magnification
Procedure
1. Students help collect and bring to school as many types of hairs and fibers as
possible. Encourage students to collect samples from barbers, hair stylists,
veterinarians, pet groomers, outdoorsmen, fabric stores, tailors, seamstresses, etc.
2. Students should take care when collecting and transporting their samples to
school, carefully placing known samples in clearly marked bags or envelopes.
3. In science notebooks or on index cards, students record what they know about
each known hair and fiber sample brought to class: Date and place collected,
fiber type (e.g., natural vs. synthetic), fiber description (thickness, twist, color,
microscopic structure, etc.), features such as scale patterns, measurement of key
features such as the width of fiber
Collecting evidence
Students collect their evidence from home, the neighborhood community, the school, or
the classroom environment. To simulate the techniques used by forensic investigators:
Pick up a fiber or hair sample with tweezers or tape, and carefully place it in a small
envelope for later analysis. If envelopes are not available, students should create a
makeshift envelope that will hold the sample securely: Place the hair or fiber in the crease
of a piece of paper which is folded lengthwise again. Then tuck the outer ends in on
themselves, Remind students to label each envelope. Example: “Thread of fiber from seat
at Regal Theatre. June 11, 2010.” Or, “hair from Uncle Wally’s couch. July 4, 2012.
Equip each student with a clean glass microscope slide. Students place a 2-inch piece of
clear tape on top of the fibers they are interested in recovering. Students place the fibers
on the microscope slide and remove the tape. After placing the slide in a labeled
container, the students transport the sample to the (classroom) “laboratory.”
Analyzing evidence
Students can use a magnifying lens in the initial stage of fiber examination. Placing the
sample against a contrasting background under the reflected light of a desk lamp will help
students determine the color of the hair.
To prepare a permanent slide for an optical microscope:
1.
2.
3.
4.
Pour a small amount of corn syrup into a paper cup.
Using tweezers, pick up a fiber sample from one of the collection envelopes.
Place the fiber on a clean microscope slide.
Use a medicine dropper to add a single drop of light corn syrup on top of the
fiber. (If water is used instead of light corn syrup, the slides can be used over
again; corn syrup is used for the creation of permanent slides.)
5. To remove any air bubbles from the slip, slowly lower the cover slip at an angle
over the drop of liquid. If the slide is a permanent one (made with light corn syrup
instead of water), use a permanent marker to label the slide. Include a sample
name and case number for each slide.
Examining slides under an optical microscope:
1. Begin by using the lowest objective magnifying power available. If the lowest
objective magnifying power is 4X, this means that the total magnification of the
image is 4 times 10 (assuming 10 is the power of the eyepiece lens). Since 4 x 10
= 40, the total magnification of the sample will be 40 times.
2. Position the objective lens so that it is over the hole in the stage.
3. To make room for the microscope slide, turn the coarse adjustment knob so it
raises the 4X objective up from the stage about 2.5 cm.
4. To send light through the sample, adjust the mirror or light source. You should
see a round, bright circle of light.
5. Place the prepared microscope slide on the stage of the microscope. Center the
sample over the hold in the stage and secure the slide with stage clips.
6. CAREFULLY lower the objective down by turning the coarse adjustment knob
clockwise. Do this as you watch it from the side.
7. Now look through the eyepiece as you turn the coarse adjustment knob so the
objective moves upward again. This time you are bringing the image into a
general focus.
8. To bring the image into a sharper focus, use the fine adjustment knob. If you need
to center the image of the fiber, move the slide on the stage.
9. For optimal contrast of light, adjust the iris diaphragm. For higher magnifications,
widen the diaphragm opening to allow more light to enter. Or adjust the disc
diaphragm if your microscope has a disc diaphragm instead of an iris diaphragm.)
10. For greater magnification, turn the revolving nosepiece to the next higher power
objective.
11. Use the fine adjustment knob to identify fibers in question (Q).
See “Create a Reference List for the Phenom SEM” for directions on preparing
permanent sample stubs for use with the table top scanning electron microscope.
For more information on creating a reference collection of hair and fiber
(This was the original source of this lesson)
http://www.alittlecreation.com/alliance/lesson2.html
a lesson on collecting hair and fur
10.
SAMPLE PREPARATION for the PHENOM
Note: Detailed instructions can be found in the original Phenom User’s Manual. The owner of
this Phenom should read the safety precautions thoroughly before preparing samples or teaching
older students how to do so.
FIRST:
1. Don’t ever poke the Phenom with anything other than a finger.
2. Don’t ever put anything wet inside the Phenom.
3. Don’t ever put anything inside the Phenom that is not totally secured to its
sample stub.
Why the precautions?
Inside the SEM strong magnetic fields forcefully guide a beam of electrons
through a vacuum chamber, down towards your sample. That magnetic force
is strong enough to dislodge anything you’ve put in there that is either wet or
loosely attached. Any debris jarred loose from the sample stub will find its
way back up the column and damage the tool. The warranty on the Phenom
probably doesn’t cover samples that have been improperly prepared. Nor
does the warranty cover damage caused by poking the screen with sharp or
pointy objects.
Materials needed for proper sample preparation
Sample stub (less than 1” diameter)
Stub-gripping tweezers
Standard tweezers
Sample tray for holding stubs during sample preparation
Toothpick (or something pointy and disposable)
One of the following: colloidal graphite, silver paint or double-sided carbon adhesive
pads
Prepare SMALL samples
Use tweezers to peel the coating from a double-sided adhesive pad. Then place a clean stub on top of
the pad so the adhesive pad sticks to the stub. Place your sample on top of the exposed sticky side.
To prepare SMALL samples such as pollens, powders, TEM grids:
1. Place a standard SEM stub into the sample tray (NEVER prepare a
sample in the Phenom cup! Any loose particle can damage the inside
mechanism.)
2. Using tweezers, peel back the coating that is on top of a piece of
double-sided adhesive pad.
3. Place a clean stub on top of the exposed adhesive pad.
4. Pull the stub off the adhesive pad to expose the other side of the
adhesive sheet.
5. Place the sample on top of the exposed adhesive pad.
6. Double-check: Is the sample firmly attached to the stub?
Prepare REALLY SMALL particles
After applying really small samples with a toothpick, tap off the loose particles from the sample stub.
Then spray the surface of your sample with compressed gas to remove further debris.
To prepare REALLY SMALL particles or samples containing small pieces
that could come loose during imaging (i.e., powders, pollen, small filings,
diatomaceous material, dust-like matter):
1. Attach a double-sided adhesive pad to a bare sample stub.
a. Using tweezers, peel back the coating that is on top of a piece
of double-sided adhesive pad.
b. Place a clean stub on top of the exposed adhesive pad.
c. Pull the stub off the adhesive pad to expose the other side of the
adhesive sheet.
d. Pull the stub off the adhesive pad to expose the other side of the
adhesive sheet.
2. Collect some of your particle sample onto the tip of your toothpick.
3. Brush the sample coated tip against the exposed adhesive of the
sample stub.
4. Using the flat side of your toothpick, press the particles firmly against
the adhesive pad.
5. Remove loose particles from the sample stub:
a. Using tweezers, grip the stub.
b. Invert the stub over a safe receptacle. Shake loose particles into
the receptacle.
c. Forcibly tap the stub on the side of a table or bench to remove
loose particles from your sample stub.
d. With a can of compressed gas, spray the surface of your sample
to remove further loose particles or debris.
e. Look again: Inspect the stub to verify that your sample is firmly
affixed to the adhesive pad.
Your sample can now be placed inside the Phenom.
Note: Repeat steps 5c and 5d when imaging a sample that has already been
prepared for you or when re-imaging a particle sample that you have already
prepared before (“Imaging” means to view a sample with the Phenom).
Prepare LARGE samples
Use a toothpick and conductive paint
for large samples.
Dab the conductive paint onto a bare stub. Then
move quick before it dries!
To prepare LARGE samples such as polymers, insects, MEM’s devices:
1. Place a standard SEM stub into the sample tray (NEVER EVER
prepare a sample in the Phenom cup! See the introductory
precautions).
2. Cement the large sample with colloidal graphite or silver paint.
a. Open the bottle in a well-ventilated area.
b. Dip your toothpick into the silver paint or graphite.
c. Dab the residual silver paint or graphite onto the bare stub.
d. Put the lid back on the silver paint or graphite.
e. Move rapidly now as the liquid dries quick!
f. Using standard tweezers, firmly clamp your sample.
g. Move the sample to a bare area of the stub. (Do not place the
sample directly into the liquid.)
h. Gently slide the sample into the drop of liquid so that the liquid
beads around the bottom of the sample.
i. Once you have attained a desired level of surface contact with
the liquid, let it dry for about 10 minutes. Your sample will be
ready to image (view) after it dries.
To Prepare Polymers (plastics, glass, or polymer coatings on a substrate
material)
o Mount them flat or on a cross section using colloidal graphite, silver
paint, double sided carbon pad or a clamping mechanism.
o Sputter coat them for best resolution.
o For polymer samples in cross-section, you may use a clamping stub.
Just be sure the sample is firmly clamped in the stub before you
sputter coat it.
To prepare metals
o Firmly fasten the sample to the stub using the procedures described
for preparing powders. For large metal filings, use colloidal graphite
or a clamping stub.
o Remember there are powerful electromagnets inside the SEM. Take
extra precaution when mounting ferrous or iron samples so they do
not pull loose from the stub during imaging.
To prepare biological samples
o Air dry the sample to remove extra moisture. Then sputter coat it for
best results.
For more information on preparing samples for the Phenom:
Phenom User Manual produced by FEI company 2008
5350 NE Dawson Creek Drive Hillsboro, OR 97124
http://www.fei.com/uploadedFiles/Documents/Content/2008_05_PhenomSamplePreparat
ion.pdf
the original sample preparation guide for the Phenom
http://www.phenom-world.com/productinformation/phenom.php#http://hwcdn.net/b3d9w2e7/cds/phenom/FEI_tv_SamplePrep.fl
v
video showing proper sample preparation.
http://www.phenom-world.com/product-information/phenom.php#movies
links to other videos featuring the Phenom
http://www.phenom-world.com/productinformation/phenom.php#http://hwcdn.net/b3d9w2e7/cds/phenom/sample-charging.flv
an explanation of “sample charging”
11. HAIR ANALYSIS PART ONE: DISCOVERY
Objective
Students use critical thinking skills to develop a systematic procedure for analyzing and
identifying unknown samples of hair.
National Science Content Standard A: Understandings about Scientific Inquiry
Rationale
Many of the strategies used for solving problems can be applied to all curricular areas. In
science --- just as it is with math, literacy, or social studies --- pattern-searching is often
at the heart of the challenges that involve solving problems. In this exploratory activity
students engage in pattern-searching as they develop a system for analyzing hair.
Materials
Hairs from a variety of species and individuals (suggestions provided)
Prepared Phenom sample stubs of hairs (to correspond with the microscope slides)
Microscope slides and cover slips
Water and droppers
Microscopes
Phenom table top SEM
Student handouts: Charting unknown hair
Students work in small groups of 2-4. Each small group will need a set of prepared slides:
Suggested set includes:
1. human hair (red, long, curly)
2. dog hair (black and straight)
3. cat hair (grey, long)
4. deer hair
5. dog hair (white, wiry)
6. cat hair (beige, short)
7. human hair (brown, straight, short)
8. rabbit hair
9. human hair (blond, wavy, long)
10. horse hair
Hook and Focus
Teacher provides the following directions:
1. “Pull out a long strand of hair from your head.
2. Hold the hair by the root between your left thumb and left index finger.
3. Use your right index finger and thumb to slide the hair from the root to the tip.
4. Now slide the hair from the tip to the root using your left thumb and index finger.
5. Which direction did you feel the greatest resistance? (Allow response)
6. Teacher explains: “What you’re feeling when you draw the strand from the tip of
the hair to the root are tiny scales that overlap each other. The overlapping scales
point toward the edges of the tip. These scales form the cuticle of your hair, one
of the three main structures you’ll be examining as you consider ways to organize
and categorize unknown samples of hair.”
7. Teacher issues student handout and prepares students for the activity. Procedural
directions are explained in the student handout.
For more information on hair analysis
http://library.thinkquest.org/04oct/00206/lesson.htm
This is the original lesson source. Includes a simulation on blood analysis.
http://www.ehow.com/about_5445024_importance-hair-evidence-forensics.html
general overview of how hair is used as forensic evidence. Easy reading.
http://www.trutv.com/library/crime/criminal_mind/forensics/trace/4.html
“caught by a hair” story from real life
Directions to help you distinguish between unknown samples of hair
1. Examine each set of labeled slides under a microscope. Also view each
corresponding sample at the optical and electron setting of the Phenom
SEM.
2. Locate and examine the three primary structures of each strand of hair
(cuticle, cortex, medulla).
Cuticle: the thin outer coating comprised of overlapping scales.
Cortext: protein-rich structure surrounding the medulla; contains
pigment.
Medulla: central core (may be absent)
3. There are two basic types of criteria you will need to consider
objective criteria can be measured. Examples of objective criteria
include length, width, or light absorbance.
subjective criteria depends upon the judgment of the observer.
Examples of subjective criteria include color, texture, and shape.
4. More information on the structure of hair will be provided later. In the
meantime, respond to the questions given below as you examine samples of
hair.
Directions: Answer the following questions and record your answers in your
science journals.
1. How does the cuticle differ among the
a. different species?
b. different individuals of the same species?
c. Try to list both objective and subjective criteria for
differentiating the cuticle of different species.
2. How does the cortex differ among hair of
differentiating the cortex of different species.
3. How does the medulla differ among hair of
differentiating the medulla of different species.
4. What other characteristics of the hairs differ between species or
individuals? Would you classify them as objective or subjective?
13. HAIR ANALYSIS PART TWO: LECTURE
Objective
Students engage in a cooperative Jigsaw learning strategy as they learn to distinguish
between the components of animal and human hair.
National Science Teaching Standard B: Teachers of science guide and facilitate
learning. In doing this, teachers challenge students to accept and share responsibility for
their own learning.
Rationale
Jigsaw is a complex cooperative learning structure that is designed to promote
interdependence throughout the learning process The benefits to this strategy are many:
a)Students learn to value the expertise of others; b) they come to view differences among
peers as a way to enrich their own thinking; c) they develop leadership and negotiation
skills that promote the group’s progress; d) they can express themselves and their
intelligence in many creative ways; e)students learn to share responsibility; g) positive
relationships are developed as the group members provide mutual support; f) students of
all abilities and developmental levels are able to master requisite knowledge and skills
related to the topic of this lesson: the various components of animal and human hair.
Materials
• Handouts of reading material (Each small group receives a different portion of the
material which they are responsible for sharing with others)
• Teacher-generated study guide
Hook and Focus
Teacher asks for students to predict the most common form of trace evidence in criminal
investigations. After students respond, s/he briefly explains that hair is the most common
form of trace evidence, and in this lesson they will learn how to distinguish between the
various components of animal and human hair.
Procedure
1) Students are placed into heterogeneous learning teams comprised of various skills,
talents, and abilities. (No reading is done within these learning teams in the beginning,
but it’s important the students know who the members of their learning teams are.)
2) One member from each learning team is assigned to a different expert team. Each
expert team focuses on one particular article or area of study related to the structure of
hair. (A suggested outline is provided, although various articles from the web work too,
depending on the needs and interests of the students.)
3) The expert teams meet to read, discuss and develop expertise of their assigned article
or area of study. Each expert team masters the content of its area of focus. (This might
take a few days to accomplish, depending on the length or content of the reading
material.)
4) Once the expert teams have mastered the content within their area of focus, they
return to their original learning teams to share what they have learned. Each expert
shares what s/he learned in their expert team.
5) After each expert within the learning team shares what they have learned, the learning
team discusses questions provided by the teacher. These questions serve as a
comprehensive study guide, and includes questions or discussion topics based upon the
whole reading activity.
6) The teacher assesses individual student learning based upon the comprehensive
study guide questions s/he has provided.
For more information on hair
http://www.fbi.gov/hq/lab/fsc/backissu/jan2004/research/2004_01_research01b.htm
A detailed manual and guide for the study of human hair. Complete with attractive
microphotographs and diagrams.
http://www.fbi.gov/hq/lab/fsc/backissu/july2004/research/2004_03_research02.htm
A detailed manual and guide for the study of animal hair. Complete with attractive
http://sciencespot.net/Media/FrnsScience/Hairsfibers08.ppt#256,1,Slide 1
PowerPoint lesson complete with photos and diagrams of hairs and fibers
http://sciencespot.net/Media/FrnsScience/hairfibernotewkst.pdf
student worksheets for the above sciencespot site
http://sciencespot.net/Media/FrnsScience/hairfiber_IDlabwkst.pdf
simple worksheet for analyzing hair
http://sciencespot.net/Media/FrnsScience/hairfiberchallenge.pdf
photos of hair and fiber prepared as a worksheet for students to guess their origin.
http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric1.htm
hair and microscopy
hair as evidence
http://sciencespot.net/Pages/classforsci.html#hairsfibers
PowerPoint of hair information
http://www.crimeandclues.com/index.php/physical-evidence/trace-evidence/63-traceevidence-hair
trace evidence and hair
http://www.time.com/time/health/article/0,8599,1720520,00.html
TIME magazine article on hair and forensics
http://www.mediacy.com/index.aspx?page=AS_123
hair: old vs. new cut
http://www.microscopy-uk.org.uk/mag/artnov04macro/tchair.html
hair as seen through a fiber optics illumination system
http://www.chem.sc.edu/analytical/chem107/lab4_032205.pdf
diagrams and photomicrographs with lecture notes. Original source comes from the
fbi.gov website below
The original source of diagrams and photomicrographs seen in several sites and books.
Article by Deedricks, posted on www.fbi.gov website
hair analysis article
For more information on the Jigsaw activity
http://www.jigsaw.org/overview.htm
jigsaw
http://olc.spsd.sk.ca/DE/PD/instr/strats/jigsaw/
jigsaw
Cooper, J.M. (ed.). (2003). Classroom teaching skills (7th ed.). Boston: Houghton Mifflin.
14. HAIR: BACKGROUND NOTES (Visuals available in Section 30)
HUMAN HAIR
•
Although hair is never used as the sole indicator of guilt, it can be a strong source
of evidence, especially when used in conjunction with DNA analysis.
•
Hair is one of the most common sources of evidence.
•
“When the [comparison] microscope is coupled with DNA technologies, the
combination of these technologies [nuclear and mitochondrial DNA (mtDNA)]
profoundly affects the way forensic scientists, investigators, and prosecutors view
hair evidence”
•
First step for forensic scientists: identify and compare human and animal hairs.
Methods of collecting hair
1. Investigators can first visually identify hair using infrared or laser light sources.
They then collect the sample by hand or with tweezers. The problem with using
tweezers, however, is that the tool can damage the hair’s structure, root, or the
tissue surrounding the root. It’s the tissue surrounding the root that contains the
DNA.
2. Clear tape to lift the hair from the surface on which it is found.
3. Vacuum, especially at large crime scenes
4. Brush, scrape, shake from garments or other fabrics onto white paper where it is
then sorted for later analysis.
5. Garments or fabric are placed in a bag and shaken so the evidence falls to the
bottom of the bag.
6. Combing to extract loose hairs and clipping the hair from the victim or suspect.
Physical characteristics of human hair
•
Definition: “slender, thread-like outgrowth from a follicle in the skin of
mammals.”
•
Hair is composed primarily of keratin. Its three morphological regions include the
cuticle, medulla, and cortex.
•
Hair grows on different regions of the body. Under a microscope hairs can be
identified according to the region of the body from which they grow. Forensic
scientists primarily compare hair from the head and pubic regions.
•
Hair grows from its papilla. Beyond the papilla, hair consists of dead, cornified
cells.
•
The root is imbedded in the skin, with the lower end expanding to form the root
bulb. The shaft projects above the skin.
•
Hair is comprised of a protein called keratin, a pigment called melanin, and a
trace amount of metallic elements that are deposited and absorbed by the hair by
cells around the follicle during its growth. The external environment also deposits
materials into the hair shaft which is then absorbed by the hair as it grows.
•
Hair actively grows during the anagen phase. The majority of hairs (roughly 85%)
on a healthy scalp are in the anagen phase. A hair on the scalp grows for about 3 –
6 years.
•
Hair rests during the telogen phase. Roughly 15% of hairs are in this resting
phase. Hair rests for about 3 – 6 months. During this resting phase, the hair is held
stable in the follicle only be the club-shaped root where it eventually falls out and
is replaced by the next generation of new, growing hair.
•
The phase between the period of growth and rest of a hair is called the categen
phase. About 2% of all hairs are in this phase at a given time. Hair in the categen
phase lasts up to 6 weeks.
•
Each day about 10% of the hair on a human scalp is in the resting phase. Humans
lose about 100 hairs a day.
STRUCTURE of the HAIR
It helps to think of a pencil when discussing a cross-section of hair:
•
•
•
The medulla can be likened to the lead. The medulla is classified as either absent,
fragmented, interrupted, or continuous. Most human hair, has either no medulla or
a fragmented one. Only Asians have a continuous medulla. The medulla is less
than 1/3 the diameter of the whole shaft of hair.
o In animals, the medulla is over ½ the diameter of the hair.
The cortex can be likened to the wood of the pencil. It’s the microscopic
structures within the cortex that forensic scientists often compare. Within the
cortex are structures such as pigment granules and air bubbles (fusi).
The cuticle can be likened to the thin layer of paint on a pencil. The species of an
animal can be determined by observing the scale patterns found on hair cuticle.
Human hair displays scales which overlap in no apparent pattern. This type of
scale is called umbricate. Petal scales look like the scales of a reptile, and are not
found on human hair. Coronal scales also, are usually not found on human hair.
Coronal scales overlap one another and form a symmetrical pattern.
3 parts of a single strand of hair
Root, shaft, tip
Root: also known as the bulb. The shape of the root determines the stage of growth and
whether the hair fell out naturally or was pulled out. If it was pulled out, the root may
also contain tissue which can be used for DNA testing.
Shaft: the shaft is examined using a compound microscope and backlight. Investigators
look at the medulla’s shape and type, the patterns of pigment granules, and the patterns
and shape of the scales on the cuticle.
Investigators also look at the damage on the shaft. For example, knowing that hair
grows one mm per day allows investigators to determin how much time has elapsed since
a person last dyed their hair.
Tip: If the tip of a hair reveals chemical or heat treatment, investigators will know it
came from the scalp. If the ends are blunt, the hair probably came from a beard that was
shaved or clipped.
What do investigators look for when examining hair samples?
•
Hair is one of the most common sources of evidence.
•
By comparing medullas and scale patterns of the cuticle, investigators can
distinguish between human and animal hairs, the first step in the process.
•
Under a microscope hair looks different from different regions of the body.
•
By looking at the shape of the bulb, investigators can tell whether hair fell out
naturally or was pulled out.
•
Pigment granules reveal patterns of color.
•
If the shaft curls or bubbles investigators can tell whether the hair was crushed or
burned.
•
Knowing hair grows one millimeter per day allows investigators to estimate the
approximate time of dye, perm, or exposure to other chemicals.
•
If the tip of the hair reveals chemical or heat treatment, the investigators will
know the hair is from the scalp.
•
If the end of the hair is blunt from a shave or clipping, the investigators will know
the hair came from a beard.
•
Forensic scientists can determine what stage of growth a strand of hair is in by
examining the root area.
•
Hairs which are shed naturally, such as through combing, will display clubshaped roots. Hair that has been pulled out, however, will display a damaged root.
Hair that has been pulled out will also show signs of being forcibly stretched.
•
Forensic scientists can determine if a hair originated from an animal or human by
comparing the scale patterns of the cuticle: Petal scales are not found in humans;
coronal scales are rarely found in humans; umbricate scales are always found in
humans.
•
Hair that has been pulled from the scalp will contain tissue around the bulb. DNA
can be extracted from the tissue to determine the victim’s sex and other genetic
information.
•
Dark bands that appear near the root of the hair occur on bodies that are in a state
of decomposition.
How do forensic investigators distinguish hair from different areas of the body?
•
The general morphology of the hair determines from what area of the body the
hair originated. Scientists study the length, shape, color, stiffness, curliness, and
microscopic appearance of the hairs in question.
•
Head hairs are usually the longest. They are uniform in diameter and often have
tips that have been cut. Head hairs have often been altered as a result of dyes,
rinses, permaments, frosts or other chemical treatment. Hair can also be altered
from exposure to sun, wind, or dry air. Forensic scientists usually obtain at least
25 random head hairs from different areas of the scalp when making comparisons.
•
Like head hairs, pubic hairs are one of the most common types of body hair
compared in the forensic labs. Pubic hairs are usually coarse and wiry, have either
a continuous or discontinuous medulla, and exhibit a wide variety of diameter size
or buckling.
•
Facial hair is also coarse, having a triangular cross section. When seen under a
microscope, facial hairs exhibit troughs. Facial hair also exhibits wide medullas
and razor-cut tips.
•
Limb hairs are shorter, shaped like an arc, and are often tapered at the tips. The
medulla is trace to discontinuous, and the pigment looks granular under a
microscope. Limb hairs are not considered valuable for comparison purposes.
•
Fringe hairs, such as those found on the neck, sideburns, abdomen, upper leg or
back, are usually not considered suitable for comparison purposes.
•
Other body area hairs such as those from the underarm, eyes, and nose, are not
usually compared during an investigation. But as with all hairs, their presence
might lend support for other areas of the investigation.
Determining race
Forensic examiners can distinguish between the hairs (usually from the head) of people
from European ancestry, Asian ancestry, and African ancestry.
European ancestry:
• usually fine to medium coarseness;
• generally straight or wavy
• colors range from blond to brown to black
• cross sections of hair shafts vary from round to oval
• pigment granules are fine to medium-sized and are evenly distributed
Asian ancestry
• regularly coarse, straight, circular cross section
• wider diameter than the hairs of other racial groups
• cuticle thicker than the cuticle of African and Asian cuticle
• medulla is continuous and wide
• cortex contains pigment granules that are usually larger than those of European
hairs
• pigment gives the hair a reddish appearance
African
•
•
•
•
•
•
•
•
regularly curly or kinky
flattened cross section
appears curly, wavy, or coiled
pigment granules are larger than those of Asian and European
pigment granules are grouped in clumps of varying sizes and shapes
pigment in the hair shaft is dense, appearing opaque
twisting or buckling of the hair shaft might be present
hair shaft often splits along the length
Age and Sex
•
Hairs of infants are usually finer and less distinctive when viewed under the
microscope. Hairs of the elderly often lose pigment, and the diameter of the hair
shaft often becomes more variable. Otherwise, microscopic examinations of hair
do not allow forensic scientists to determine the age of the individual.
•
The sex of the individual is also difficult to determine from microscopic analyses,
although females usually have longer hair and hair that has been chemically
treated. To determine the sex of an individual, scientists can stain the sex
chromatin found within the follicular tissue cells. To obtain more specific
information on the origin of a hair, scientists can analyze the nuclear and
mitochondrial DNA (mtDNA).
ANIMAL HAIR
•
Animal hairs are classified according to three types: 1) guard hairs that form an
outer coat to protect the animal, 2) fur or wool hairs that form the inner coat,
providing insulation, and 3) tactile hairs (whiskers) found on the animals head to
provide it with sensory functions.
•
In addition to the three main types of hair, tail hair and mane hair are also found
on certain animals.
•
The medulla of most animals is continuous or interrupted.
•
Animal hair is first identified by animal type and then compared microscopically
with either a sample from a specific animal or from an animal reference
collection. If the questioned hair (Q) reveals the same characteristics of the hair
that is known (K), then investigators conclude the hair is consistent with
originating from the animal in question.
•
Before comparing animal hairs, a large enough sample from every area of the
animal’s body should be collected. This is because animal hairs vary widely in
color and length. Hairs from an animal should be both combed and plucked;
taking samples from the animal’s brush or comb works also.
•
The hair on different species of animals exhibit different patterns. For example,
rabbit hair exhibits uni or multiserial ladders. Deer exhibit lattice patterns.
How do forensic scientists observe the different patterns of hair?
They make a cast of the outer scales by placing the hair in a liquid much like clear nail
polish. After the liquid hardens, the hair is removed so they can study the impression left
behind.
15. I-SEARCH ACTIVITY
Objective
Students conduct research related to a career or topic of interest to them.
National Science Content Standard F: Science and technology in society.
National Science Content Standard G: Science as a human endeavor.
Rationale
Adolescents exposed to scanning electron microscopy are more inclined to consider
fields of work related to science, technology, engineering, and math. The I-Search Paper
(Macrorie, 1988), a more engaging, meaningful form of the traditional research paper,
allows students to choose a relevant research topic, conduct interviews, include
“nontraditional” sources of information, and document the process of their research and
problem-solving.
Procedure
I-Search Paper
Original source: Macrorie, K. (1988). The I-search paper. Portsmouth, NH: Heinemann
1. Students, working individually or in small groups, choose a unit topic that is of
personal interest to them. (A list of possible research topics is provided.)
2. Students generate a list of possible sources of information, especially the experts
or more knowledgeable others that they might interview.
3. Students design interview questions based upon the information they are
interested in learning, whether or not it relates directly to the expert’s job.
4. Students conduct the interviews and also pursue additional sources of
information, whether traditional or nontraditional.
5. The students write their papers in narrative form, describing the process they went
through while researching their topic.
6. Within the body of the I-Search paper, students should include the following four
categories of information:
a. What you knew and did not know about the topic before conducting the
search
b. Why you decided to research this particular topic
c. A description of the search
d. A description and discussion of what you learned.
e. List of all resources
Possible I-Search topics
Careers related to forensics
medical examiner
crime laboratory analyst
crime scene examiner
forensic engineer
academic assistance –
psychology (including psychological profilers)
social science
statistics
technical assistance
computer analyst
polygraph
composite drawing
photography superposition
forensic skull reconstruction
computer image enhancing
voice and diction analysis
account auditing
polygraph examinations
forensic art
forensic pathology
forensic accounting
forensic toxicology
forensic anthropology
computer forensics
forensic odontology
forensic linguistics
forensic entomology
forensic animation
forensic photography
forensic nursing
forensic psychology
forensic psychology
forensic science technician
medicine
legal medicine
public health
autopsy
toxicology
pathology
epidemiology
genetics
infectious disease
physical biology
chemistry
engineering
education
archeology
geology
odontology
document analysis
graphology
Crime Lab Analyst I
Crime Scene Analyst
Criminalist
Crime Lab Director
DNA Analyst
Evidence Custodian
Firearms Examiner
Fingerprint Technician
Forensic Autopsy Assistant
Forensic Autopsy Technician
Forensic Biologist
Forensic Evidence Technician
Forensic Scientist
Law Enforcement Training Officer
Latent Print Examiner
Latent Print Technician
Toxicologist
Trace Analyst
Police sketch artist
Instruments and tools used in the analysis of trace evidence:
Stereoscopic Microscopy
Polarized Light Microscopy (PLM)
Ultraviolet Light Microscopy
Scanning Electron Microscopy (SEM/EDX)
Fourier Transform Infrared Spectroscopy (FT-IR)
Gas Chromatography / Mass Spectrometry (GCMS)
Pyrolysis Gas Chromatography (PGC)
Ion Chromatography (IC)
Microspectrophotometry
From http://definitions.uslegal.com/t/trace-evidence/
Degrees related to forensic science
criminal justice
criminal investigations
crime scene investigation
cyber crime
forensic science
homeland security
computer crime
forensic psychology
For more information on topics students might choose to research
http://csidegrees.com/jump/crime-scene
investigation/index.php?s=msn&k=forensic%20science%20degree&ss=fmuonlineuoponline&c=campaignname
includes pay information
http://definitions.uslegal.com/t/trace-evidence/
instruments and tools used in the analysis of trace evidence
http://csidegrees.com/jump/crime-scene-investigation/index. php?s=msn&k=
forensic%20science%20degree&ss=fmuonline-uoponline&c=campaignname
includes degrees related to forensic science
http://www.all-about-forensic-science.com/forensic_jobs.html
jobs. Good link, although it doesn’t list the jobs straight out. More of a resource board.
http://www.forensicartist.com/links.html
lists several links to the topic of forensic art
http://www.forensicartist.com/
forensic art certification site
http://www.all-about-forensic-science.com/forensic-science-careers.html
careers in the forensic sciences. The little videos and photos are informative.
http://aafs.org/default.asp?section_id=resources&page_id=choosing_a_career#Bookmark
1
tells all about forensic science as a career. Lists resources – relevant organizations that
would be good for research.
http://www.guidetocareereducation.com/criminal-justice/forensic
paragraph describing the increase in need for forensic science technicians by 2016
http://dsc.discovery.com/videos/human-forensic-entomologist.html
Discovery clip on forensic entomologist. Interesting. Brief interview.
http://www.all-about-forensic-science.com/forensic-linguistics.html
fascinating re: linguistics and crime
http://english.forensischinstituut.nl/
Nederlands Forensisch Instituut.
http://www.crime-scene-investigator.net/JOB-08-10-05.html
Job description for Forensic Scientist I, Oregon State police
http://www.enotes.com/forensic-science/training
info on the training required to enter forensics
http://www.youtube.com/watch?v=p9lHGp5rlJg&NR=1
ACFEI names a few specialist fields
http://www.youtube.com/watch?v=DsTsPWH-clo
advertises a course at Lancanshire, but good
http://www.youtube.com/watch?v=TDKf3KgeAPc&NR=1
attorneys and forensic experts – certified forensic consultant
somewhat slow, but might be of interest to kids interested in law/lawsuits
http://www.youtube.com/watch?v=kEkk13J3Ylk
brief explanation of how forensic scientists are in the lab whereas the investigators are on
the scene of the crime.
resource board for jobs related to forensic science.
16. HAIR ANALYSIS PART THREE: ANALYZE
AND IDENTIFY UNKNOWN SAMPLES OF HAIR
Objective: Students analyze and identify unknown samples of hair.
National Science Content Standard A: Use technology and math to improve
investigations and communications
Rationale: Teachers of science understand that investigations must be meaningful to
students if students are to engage in deep learning. Students will find increasing value,
relevancy and meaning in activities that require active and continued involvement and
increasing challenge. In Part Three of this lesson on hair analysis, students actively
compare and contrast “evidence” while sharpening their skills of observation and
analysis.
Materials
Hairs from a variety of species and individuals (suggestions provided)
Microscope slides and cover slips
Water and droppers
Microscopes
Student handouts: Charting unknown hair
Students work in small groups of 2-4. Each small group will need a set of prepared slides:
Suggested set includes:
11. human hair (red, long, curly)
12. dog hair (black and straight)
13. cat hair (grey, long)
14. deer hair
15. dog hair (white, wiry)
16. cat hair (beige, short)
17. human hair (brown, straight, short)
18. rabbit hair
19. human hair (blond, wavy, long)
20. horse hair
Advanced preparation required by teacher:
For each group, the teacher prepares a set of four envelopes, labeled and filled according
to the specifications below:
Labeled Envelope
Suspect A
Suspect B
Contents of Envelope
packet containing 20 hairs from Human #1
packet containing 20 hairs from dog
packet containing 20 hairs from Pet #3
(Note: The pet hair found with Suspect B should be the same as that found with the
evidence in the evidence envelope.)
Suspect C
Evidence
packet containing 1 hair from Human #2
packet containing 1 hair from Human #3
packet containing 1 hair from Pet #3
(Notice the pet hair from Pet#3 is the same as the pet hair found with Suspect B.)
For more information on analyzing and identifying unknown samples of hair. (See
also the reference list in Part Two of this lesson)
This is the original lesson source. It also includes a simulation on blood analysis.
COMPARING EVIDENCE
Directions
In envelopes A, B, and C are hairs taken from three different suspects. Envelope D
contains hairs from the crime scene.
Your task is to work together as a team to examine and compare the suspects’ hair
samples to the sample take from the crime scene (“evidence”).
1. Open Envelope A and the first packet inside to remove one or two hairs.
2. Measure the length of the hair in millimeters and record.
3. Prepare and label a set of slides for each envelope provided.
4. Make a wet mount of each hair using the labeled slide.
a. Place a small drop of water on the center of the slide.
b. Place the appropriate hair in the drop of water so that the hair lies flat on
the side. Cut a small length of hair if necessary.
c. Cover the hair and water drop with a cover slip.
5. Examine each slide under the microscope at high power. Fill out the data sheet for
each hair, adding criteria where needed.
HAIR ANALYSIS DATA SHEET
Label
Date
Characteristics
Description
Length (mm)
Color
Condition of root (bulbous, rounded, pointed, attached bits of skin, etc.)
Condition of tip (frayed, smooth, bent, split, etc.)
Width (if microscope is fitted with a micrometer)
Cuticle scales (flat and smooth, protruding, spiky, etc.)
Medulla (present/absent, broken, continuous, thick, thin)
Width of medulla (exact measurement and/or medullar index –ratio of width to entire
diameter of hair’s cross section)
Possible species identity (see database)
Remember that hair alone cannot establish the guilt or innocence of a suspect. However,
when provided with additional evidence, hair CAN corroborate (support) other physical
evidence.
Given the results of your analysis, submit a report describing your results.
18. Notes on forensic fiber examination from the FBI website
http://www.fbi.gov/hq/lab/fsc/backissu/april1999/houckch1.htm
Note: The following notes have been written verbatim from the original <www.fbi.gov>
website, although some of the original content has been omitted for the sake of brevity.
Microscopy
At a minimum, a fiber examiner must employ a stereomicroscope, a comparison
microscope, and a compound light microscope equipped with polarized light capability.
The examiner must view questioned and known fibers side by side at the same
magnifications in visible light, and alternative lighting, such as polarized light or
fluorescent lighting, although not necessary, is recommended if the equipment allows.
Comparison
Typically, fiber examinations involve a comparison of samples from known and
questioned sources to determine whether they are consistent with having originated from
the same source (e.g., carpet from a suspect's car compared with foreign fibers removed
from the victim's clothing).
Source Determination
Textile fibers can be exchanged between individuals, between individuals and objects,
and between objects. When fibers are associated with a specific source, such as fabric
from the victim, suspect, or scene, a value is placed on that association. The probative
weight of this value is dependent upon many factors. The following subsections describe
those factors.
•
•
•
•
•
•
•
•
Fiber type or types found
Fiber color or colors
Number of fibers found
Fiber location or locations
Fabric type or types
Multiple fiber associations
Nature of contact
Fiber transfer and persistence.
Whether a fiber is transferred and detected is also dependent on the nature and duration
of the contact between the suspect, the victim, or both and the persistence of the fibers
after they have been transferred.
Fiber Type or Types. The rarity or commonness of the fiber types found at a crime scene
or on a victim or suspect affects their probative value. Cotton fibers are by far the most
commonly used plant fibers in textile production. The type of cotton, the fibers' length,
and the degree of twist contribute to the diversity found in cotton fibers. Processing
techniques, such as mercerization, and color applications also influence the value of
cotton fiber identifications. The presence of other less common plant fibers at a crime
scene or on the clothing of a victim or suspect increases its significance.
The most common animal fiber used in textile production is wool originating from sheep.
The fineness or coarseness of woolen fibers often dictates the end use of wool. The finer
woolen fibers are used in the production of clothing, whereas the coarser fibers are found
in carpet. The diameter and the degree of scale protrusion of the fibers are other
important characteristics. Woolen fibers from other animals may also be found, including
camel, alpaca, cashmere, and mohair. The identification of less common animal hairs,
fibers, or both at a crime scene or on the clothing of a suspect or victim would have
increased significance.
Over half of all fibers used in the production of textile materials are manufactured. Some
manufactured fibers originate from natural materials such as cotton or wood, whereas
others originate from synthetic materials.. Polyester and nylon fibers are the most
commonly encountered manufactured fibers, followed by rayons, acetates, and acrylics.
There are also many other less commonly manufactured fibers. The amount of
production, the end use, the cross-sectional shape, microscopic characteristics, and other
traits of the fiber help to influence the degree of rarity of a particular fiber type.
Fiber Color or Colors. One of the greatest variations seen in textiles is color. Thus, color
greatly influences the significance of a fiber comparison. Given that the total annual
production of any particular dye might not amount to more than 10 tons and that small
process batches are becoming the rule in the dyeing industry, color becomes a powerful
discriminant.
Individual fibers can be colored before being spun into yarn, yarns can be dyed after
being spun, or the fabric can be dyed before or after its construction. Color can also be
applied to the surface of a fabric by printing. The absorbance of the dye along the fiber
length suggests the dyes and dyeing method used. Fading and discoloration may also add
increased significance to a fiber association.
Number of Fibers. The number of fibers identified on the clothing of a victim associated
to the clothing of a suspect is important in determining actual contact. The greater the
number of fibers, the more likely that direct contact occurred between these individuals.
But finding no fibers does not necessarily mean that no contact occurred. Each case is
different, and the examiner must weigh all of the relevant factors before determining the
significance of the evidence.
Fiber Location. Where the fibers are found also affects the probative value of a particular
fiber association.
Fabric Type. Fabric construction affects the number and types of fibers that may be
transferred. Tightly woven or knitted fabrics shed fewer fibers than loosely knit or woven
fabrics. Fabrics composed of filament yarns shed less than fabric composed of spun
yarns. Certain types of fibers also transfer more readily. The condition and wear of the
fabric also affects the degree of fiber transfers: Newer fabrics may have an abundance of
loosely adhering fibers on the surface of the fabric, whereas worn fabrics may have
damaged areas that easily shed fibers. Damage to a fabric caused during physical contact
greatly increases the likelihood of fiber transfer.
Multiple Fiber Associations. If many different fiber types are associated among the
suspect, victim, and scene, then the likelihood that contact occurred between these items
is greatly increased.
Nature of Contact. The type of physical contact between a suspect and a victim helps to
determine the number of fibers transferred and the value placed on their discovery.
Fiber Transfer and Persistence. Textile fibers are transferred to the surface of a fabric
either by direct (primary) transfer or indirect (secondary) transfer. The likelihood of
transfer depends on the types of fabric involved in the contact and the nature and duration
of the contact. it is important for investigators to retrieve clothing immediately.
Whenever a fiber is found in relation to a crime scene, victim, or suspect, it has potential
significance. Matching dyed fibers, whether manufactured or natural, can be very
meaningful, whereas the matching of common fibers such as white cotton or blue denim
cotton would be less significant. In some situations, however, the presence of white
cotton or blue denim cotton possibly still has some meaning in resolving the truth of an
issue.
Volume of Fiber Production
It could be argued that the large volume of fibers produced reduces the significance of a
fiber association discovered in a criminal case. It can never be stated with certainty that a
fiber originated from a particular textile because other textiles are produced using the
same fiber types and color. The inability to positively associate a fiber to a particular
textile to the exclusion of all others, however, does not mean that a fiber association is
without value. Considering the volume of textiles produced worldwide each year, the
number of textiles produced with any one fiber type and color is extremely small. The
likelihood of two or more manufacturers exactly duplicating all of the aspects of the
textile is extremely remote (see endnote 2). Beyond the comments made previously about
color, shade tolerance differs between dyeing companies. Therefore, color may vary
demonstrably from batch to batch. Also, the life span of a particular fabric must be
considered. Only so much of a given fabric of a particular color and fiber type is
produced, and it will eventually end up being destroyed or dumped in a landfill.
The world produced approximately 80 billion pounds of fabric in 1995, about half of
which was cotton (5). The other approximately 44 billion pounds of fiber were
manufactured or synthetic. Table 1 provides U.S. fiber production levels.
Significance. As an example, given a yarn-dyed nylon fiber from a knit polo shirt of a
specific color, the significance could be described in the following way:
•
•
•
•
•
•
•
•
•
•
•
•
•
Total fiber production
Total nylon (of that type) production
Total nylon production in staple form
Total production of Item 3 in a particular denier, cross-section, optical
characteristics, and luster
Total amount of Item 4 used in production of garments
Total garments constructed in the same fashion, including knit specifications,
collar, and sleeve incorporating Item 5
Total of Item 6 in a specific color
Total of Item 7 from indistinguishable dye lots
Total of Item 8 available for merchandising
Total of Item 9 sold
Total of Item 10 still in existence
Total of Item 11 available to be connected with a particular criminal offense
Total of Item 12 actually connected with a particular criminal offense (i.e., found
and submitted as evidence).
The fiber examiner is still limited to stating that the questioned fibers are consistent with
originating from the evidence garment
Fiber Source
The chance of finding known fibers from a randomly selected suspect source that match
the questioned fibers is remote (see endnote 3).
Analysis
There are three basic activities involved in an analysis: (a) collection of a representative
sample; (b) preparation of the sample for analysis; and (c) analysis using appropriate
methods.
Although these activities are independent of each other, any one can have a significant
effect on another. Because error is possible at each step, the examiner must be able to
identify these errors and avoid them. Any method of analysis has certain attributes such
as accuracy, precision, specificity, sensitivity, dependability, and practicality that must be
considered when choosing the most appropriate method to adequately answer the
question at hand. Ultimately, it is the examiner's responsibility to evaluate all of the
available information and decide the level of uncertainty that is acceptable with a given
method on a given set of samples.
Physical Matches
A physical match occurs when two or more pieces of fabric or cordage are reconstructed
to prove they were previously one continuous piece of fabric or cordage. This
examination is conducted by describing and documenting any cut, torn, or damaged
edges on questioned items and their correlation to like areas on known items.
Photography is the recommended method of documentation.
Fiber Examinations
Fiber identifications requires a sufficient number of examinations to unequivocally place
the fiber in question into one and only one generic class
Fiber comparisons consist of determining if a questioned fiber or fibers exhibits the same
chemical, microscopic, and optical properties as fiber or fibers comprising part or all of a
known sample.
Report Documentation
Laboratory results should be reported in a uniform and consistent manner. The
International Organization for Standardization (ISO) recommends that reports be clear,
accurate, and unambiguous in the presentation of results .
For more information on forensic fiber examination
The notes on forensic fiber examination were taken verbatim from this website, although
some of the original content has been omitted for the sake of brevity.
19. CALCULATE THE MEDULLARY INDEX
Objective
Students use knowledge of fractions and decimals to calculate the medullary index of
hair.
National Science Content Standard A: Use mathematics in all aspects of scientific
inquiry. Use technology and mathematics to improve investigations and communications.
Rationale
The National Research Council (2008) explains the important role mathematics plays in
every aspect of inquiry: “Measurement is used for posing questions, formulas are used for
developing explanations, and charts and graphs are used for communicating results”
(p.175). To calculate the medullary index of hair, scientists and students must apply their
knowledge of fractions decimals when analyzing hair as trace evidence.
Materials
Photos or diagrams of human and animal hair as seen through a microscope (included)
Phenom (optional)
Hook and Focus
Teacher holds up a wood pencil and asks students to consider how it might represent the
hair of a human or animal. (Allow students to make connections). Teacher then explains:
The cuticle can be compared to the paint on the outside of the pencil. The cuticle
is the hard, protective covering that protects the inner layer of the hair shaft. It is made of
overlapping scales.
The cortex is the protein-rich area containing pigment granules (when present).
The cortex makes up 70 – 90% of the hair shaft in humans and can be compared to the
wood part of the pencil.
The medulla, about the same proportion as the pencil lead, is a canal that runs
through the center of the hair. It can be continuous, interrupted, or even absent in
humans.
Teacher explains that scientists must engage in a little mathematical calculation to
determine if a strand of hair comes from an animal or human, one of the first steps in
analyzing hair.
Procedure
1. Teacher displays several photos or diagrams of human and animal hair and
instructs students to work with a partner to compare the human hair with the
animal hair. What patterns do they find that might distinguish between animal and
human hair?
2. After a few moments, return students to the whole group for a brief discussion.
Students should recognize that the medulla (center canal of the hair) is much more
prominent in animal hair. Some medulla is even absent in human hair.
3. Teacher might ask students to estimate the size of the medulla compared to the
size of the entire hair shaft for animals and then for humans.
4. Teacher then provides the following information (some of which might be review
from the previous lessons on hair)
a. The medulla is composed of cells running through the center of the cortex.
In humans the medulla can be continuous, interrupted, or even absent.
b. The size of the medulla compared to the entire hair shaft is known as the
medullary index. This ratio is written as a fraction and then converted to
a decimal.
c. To convert fractions to decimals divide the fraction’s numerator by its
denominator. For humans, the medulla index is roughly 1/3 or 0.33. For
animals, the medulla is greater than ½ the diameter of the hair shaft, or >
0.50.
Examples of medullary index
Width of medulla
Width of entire hair
=
16µm
23 µm
=
0.70
(animal)
Width of medulla
=
32µm
39 µm
=
0.82
(animal)
Width of medulla
=
16µm
27 µm
=
0.59
(animal)
Width of medulla
=
24µm =
100 µm
0.24
(human)
Width of medulla
=
21µm
97 µm
=
0.22
(human)
Width of medulla
=
20µm =
106 µm
0. 19
(human)
Assessment ideas
• Given various medullary indices, students determine if the hair is of human or
animal origin.
•
Students calculate the medullary index of various samples of hair.
•
Using the Phenom, students examine and calculate the medullary index of a few
samples of hair.
For more information related to the medulla or the medullary index
background on hair as used in forensics; discusses the parts of hair
http://images.google.com/images?sourceid=navclient&rlz=1T4SUNA_en___US288&q=
medullary+index&um=1&ie=UTF8&ei=Cn4tS6_cLISusgP6s9DDBA&sa=X&oi=image_result_group&ct=title&resnum=4
&ved=0CBoQsAQwAw
photographic images of medulla (and other images related to other science topics)
http://images.google.com/imgres?imgurl=http://home.gwu.edu/~wfrowe/Jj02.jpg&imgref
url=http://home.gwu.edu/~wfrowe/cases_graphic.htm&usg=__XT2SGHr0SU25nk6xNm
UMppjf2ZM=&h=437&w=640&sz=37&hl=en&start=1&um=1&tbnid=AdUY8CseI_LtM:&tbnh=94&tbnw=137&prev=/images%3Fq%3Dmedullary%2Bindex%26hl%3De
n%26rlz%3D1T4SUNA_en___US288%26sa%3DX%26um%3D1
article using the medullary index in the context of a real situation
http://hypertextbook.com/facts/1999/BrianLey.shtml
discusses the diameter of a human hair
http://www.phenom-world.com/applications/education.php#
links to scale lesson using the Phenom
20. IDENTIFY WEAVE PATTERNS
Objective
Students identify different weave types and patterns from a variety of fabric samples.
National Science Content Standard A: Use appropriate tools and techniques to gather,
analyze, and interpret data
Rationale
As explained by the National Science Education Standards, scientists and students must
learn to define small portions of the natural and designed world if they are to understand
the larger complexities of it. Examining and categorizing fabric samples with a hand lens
will later increase student’s ability to understand the difference between fibers at the
microscopic level.
Materials
Fabric samples
Examples: cotton calicos, cheesecloth, gingham, serge, terry cloth, felt, corduroy,
denim, satin, calico, tweed, velvet, velveteen
Envelopes
Magnifying lens
Hook and Focus:
Teacher: “With a partner take one minute each to describe everything you can about your
shirt: the pattern, the texture, the weave, the threads – anything you can say about it.”
After two minutes, and before proceeding with the lesson, allow a few students to share
what they have to say about their shirt.
Procedure
Teacher: “Threads and yarns come from either natural or synthetic fiber. When threads or
yarns are interwoven together, fabric or cloth is formed. Fabric can be smooth and flat or
raised, with threads projecting outward in what’s called a pile. (Show example of terry
cloth as an example of fabric with a raised surface.)
“A forensic fiber examiner must understand all the different weave types and patterns of
both common and rare fabrics. She or he must also know what the different fabrics and
weave types are used for. Before they look under the microscope, they have to understand
something about the cloth. So that is where we begin today: with an examination of the
cloth.”
Directions:
Examine each piece of fabric. After discussing with your partners the texture, pattern, and
weave type of each, try to group the fabrics together by the pattern of the weave.
1. In small groups, students examine and discuss the surface of each fabric type,
writing descriptions of each fabric in their science journal.
2. Students then group the fabrics by the type of weave.
3. The teacher then guides the students in matching the vocabulary of the weave
type with the weave pattern and fabric, discussing with the students common uses
for each.
Weave types: plain, twill, satin, uncut pile, cut pile, felt
Suggested assessment: Given additional swatches of fabric, students correctly label the
weave pattern.
Suggested Answer Key:
Weave Type: plain.
Common fabrics: cotton calicos, cheesecloth, gingham.
Common uses: curtains, handkerchiefs, tablecloths
Weave type: twill
Common fabrics: denim, serge, tweed
Common uses: pillows, upholstery, clothing
Weave type: satin
Common fabrics: satin
Common uses: draperies, clothing
Weave type: uncut pile
Common fabrics: terry cloth
Common uses: towels, robes, carpet, area rugs
Weave type: cut pile
Common fabrics: corduroy, velvet, velveteen
Common uses: upholstery
Weave type: felt
Common fabric: felt
Common uses: crafts
For more information on weave patterns
This was the source of the lesson idea.
For more information related to weave patterns and fabrics
http://en.wikipedia.org/wiki/Plain_weave
general introduction to plain weave type
http://www.fabrics.net/cotton.asp
glossary of cotton fabrics and weaves
http://en.wikipedia.org/wiki/Twill
information on twill
http://www.cyberfiberonline.com/glossaryG.html
extensive glossary
http://www.harisons.com.my/?id=38&mnu=38
extensive fabric glossary
Chapman, G., and Robson, P. (1995). Salvaged! Art from fabric with projects using rags,
old clothing and remnants. New York: Thomson Learning.
Fourneir, N., & Fountier, J. (1995). In sheep’s clothing: A handspinner’s guide to wool.
Loveland, CO: Interweave Press.
Jerstorp, K. & Kohlmark, E. (1988). The textile design book: Understanding and creating
patterns using texture, shape, and color. Asheville, NC: Lark Books.
Mainprize, V. (Editor). (1998). Craft workshop: Fabric. New York: Crabtree Publishing
Company.
21, THE FEATURES OF FIBER
Objective
Students examine and describe fiber using the language of forensic fiber examiners.
explanations.
Rationale
The words people use to describe the world shapes their perceptions and understanding of
it. Knowing the terminology of forensic fiber analysis will help students see more clearly
and understand more deeply the subject matter they are investigating. In this hands-on
activity, students begin to apply specific terminology to fiber analysis.
Materials
Hand lens (for each student or pair of students)
Optical microscopes
Strand of cotton fiber (for each student or pair of students)
Phenom
Hook and Focus
Teacher: “Think for a moment about clothing. Clothing can be made from plant fibers or
animal fibers or synthetic (manmade) fibers. Think about the clothes that you most often
wear… What material are you wearing now? (Allow a moment for students to consider or
discuss this.)… What do you predict is the most common fiber used for clothing and other
textile products? (Allow a brief moment think time before students answer in pairs)… If
you guessed cotton, you were correct. In fact, about half of the approximately 80 billion
pounds of fabric produced each year comes from cotton. The other half is either synthetic
or manufactured material. Knowing how common it is to find cotton at a crime scene, or
knowing how rare it would be to find any particular type of fiber at a crime scene, affects
the probative value of that piece of fiber.
“Cotton, even though it is such a common plant fiber, can vary in several diverse ways: It
can vary in the type of cotton, the length of the fiber, the degree of its twist, how the
cotton is processed, and the amount and type of color that is applied to it. All of these
varying factors influence the value of the fiber’s identification at a crime scene.
“Typically, fiber examiners use different kinds of powerful microscopes
(stereomicroscopes, comparison microscopes, compound light microscopes, scanning
electron microscopes) when comparing samples from known sources with the samples in
question. Fiber is an extremely important source of trace evidence, and examiners must
be able to distinguish between all of the different types of fiber that has ever been
produced. Today we will begin examining and identifying the different features of fiber,
beginning with the most common type of plant fiber: cotton.”
Procedure
1. Teacher issues a single strand of cotton fiber to each pair of students.
2. Students examine the fiber with a hand lens. They work in pairs to describe, illustrate,
and record their observations in their science journal.
3. After a brief whole-group discussion with a few students sharing their observations,
the teacher provides additional information about fiber analysis:
4. Direct Instruction from the teacher:
Examiners look for the following physical features that characterize fibers:
Crimp (the waviness of fiber)
Length
Color
Relative diameter
Luster (the gloss or shine of a fiber that is a result of how it reflects light.)
Apparent cross section
Damage
Adhering debris
5. After discussing each concept above, the students again discuss their strand of fiber
with their partners, using any applicable terminology from the lesson. Refined or revised
observations are added to their science journals.
6. Students repeat the procedure (working together to examine, discuss, illustrate and
record their observations of the fiber) using the optical microscope.
7. Students repeat the procedure using the Phenom.
8. Whole group discussion: Help students understand the following information which
should be noted in students’ science journals:
A fiber examiner’s analytical notes include all of the characteristics of the fibers being
compared:
• the value of the evidence (for example, depending on how common or rare the
fiber)
• the description of the fiber
• diagrams
• photographs
When the characteristics of the questioned fiber (Q) and known fiber (K) are the same in
every way, the examiners say there is a “positive association” between the two. When the
questioned (Q) and known fibers (K) differ in some significant way, they say there is a
“negative association.” When no conclusion one way or the other can be reached they say
the result is “inconclusive.” For all inconclusive results, the examiners are required to
provide an explanation for why it was impossible to provide a definitive conclusion.
Assessment: Given a different type of fiber (or when shown photographs of different
types of fibers), students are able to describe the fiber using any applicable terminology
from above.
For more information on the features of fiber
a thorough introduction to forensic fiber examination; from the FBI.
http://www.imageafter.com/image.php?image=b17maartent1480.jpg
photo of cotton
http://dna-trace-analysis.suite101.com/article.cfm/forensic_fiber_analysis
brief, general introduction to forensic fiber analysis
from the trace evidence unit of the FBI
http://www.fbi.gov/hq/lab/fsc/backissu/april1999/houckch1.htm#3.0.Terminology
a thorough description of fiber analysis from the FBI website
22. DISTINGUISH BETWEEN NATURAL AND SYNTHETIC FIBERS
Objective: Making observations through the Phenom scanning electron microscope,
students are able to distinguish between natural and synthetic fibers.
National Science Content Standard A: Develop descriptions, explanations, predictions,
and models using evidence
Rationale
Scientific inquiry, the diverse ways in which scientists study and explain the natural
world, involves many skills. Making observations is one of them. Interpreting that which
is observed, and distinguishing between the microscopic particles that are observed are
both skills pertinent to the forensic scientist’s professional life. In this lesson, students
develop their observational skills in order to distinguish between fibers that are manmade
and those that are found in nature.
Materials
Each small group needs:
• A hand lens for each student
• Small strands of synthetic (man-made) and natural fibers
Synthetic fibers include acrylic, nylon, polyester, rayon, acrylic, acetate.
Natural fibers include cotton, wool, hemp, flax, camel, cashmere, mohair, alpaca.
(Note: some manufactured fibers originate from cotton, wood or other natural materials;
other manufactured fibers originate from synthetic materials.)
Hook and Focus
Teacher: “Recently we examined a single strand of cotton fiber. But you probably know
that there are actually many different types of fibers available.
“Think for a moment of all the different kinds of material – the fibers – that you know of.
In small groups, brainstorm with your partners all the different types of fibers that you
can think of. You have over 1,000 to choose from.” (Allow 2-3 minutes for small-group
brainstorming session).
Return students to the whole group and allow them to share the known fibers they listed
in their small groups.
Teacher: “You already know of several types of fibers. Fibers are often left behind at
crime scenes as “trace evidence,” and when you look at the fibers under the Phenom
scanning electron microscope, you’ll see that they can each be distinguished by their own
unique physical features. Forensic examiners use this knowledge about different fibers to
determine if a particular fiber found in one place could have come from somewhere else.
For example, if somebody’s home has been burglarized, the forensic scientists might find
a tiny strand of fiber there in the victim’s home. Using an electron microscope, she or he
could then compare the fiber found in the victim’s home with a small piece of carpet
taken from the suspect’s home. By comparing the “questioned sample” (the fiber sample
collected from the home of the victim) with the “known sample” (the small piece of
carpet taken from the suspect’s home) the examiners could then determine if there was
some kind of association between the two fiber samples, that is, if the fiber in question
was “consistent with originating from the same source” as the known sample.
“Today you will have a chance to develop the kinds of observational skills forensic
scientists employ when they compare fiber samples.”
Procedure
Students work in small groups.
1. Using hand lenses, students work together in small groups to compare the natural
fibers with the synthetic fibers.
2. Students record their results in their science journals. (Students might find it
difficult to distinguish between the fibers using only the hand lens. This first
activity and the next underscore the value of electron microscopy.)
3. Students repeat the procedure using an optical microscope or the optical setting of
the Phenom SEM. Students record their observations in their science journals.
4. Students repeat the procedure, this time using the SEM. Again, students record
their observation in their science journals, making special effort to articulate the
general physical difference between natural and synthetic fibers.
Students might review the following terminology when attempting to distinguish
between the fibers:
Crimp, Length, Color, Relative diameter, Luster, Apparent cross section, Damage,
Adhering debris
Assessment
Students’ science journals should include illustrations and details related to their
observations.
Alternative assessment
Given photos of various fibers as seen through a SEM, students can identify the unknown
fibers as either natural or synthetic.
For more information on fiber analysis
http://www.authorstream.com/Presentation/danielharvey9-167032-forensics-fiberanalysis-entertainment-ppt-powerpoint/
forensic fiber analysis power point
http://www.imageafter.com/category.php?category=fabrics
royalty free photos of fabrics
http://www.imageafter.com/category.php?category=fur
royalty free photos of fur
http://www.chymist.com/FIBER%20ANALYSIS.pdf
lesson which involves burning and dyeing tests for fibers; includes cross sections of
various fibers
fiber analysis article
23. FIBER ANALYSIS BACKGROUND INFORMATION
The fiber analysis methods used by forensic fiber examiners depend upon the sample
size, sample suitability, laboratory equipment, and examiner training.
Fiber analysis guidelines:
To ensure accuracy, precision, and production, forensic fiber examiners should utilize a
combination of methods when analyzing fibers from a crime scene. At the very least, they
should employ a stereomicroscope, comparison microscope, and compound light
microscope with polarized light capability, but a scanning electron microscope is
sometime necessary to yield even more precise results. The examiners view both the
questioned and known fiber samples side by side using the same magnification.
Examiners will typically compare known and questioned samples to determine if they
could have originated from the same source. They might compare, for example, foreign
fibers from a victim’s shoe with carpet from the suspect’s home.
Examiners compare class and individual characteristics.
When it is determined that textile fibers have been exchanged between individuals,
objects, or between individuals and objects, examiners then weigh the value of the
association between the fiber and the particular source. Finding a grain of beach sand in
the home of a known agoraphobic (one who is afraid of open places), for example, is
more significant than finding a grain of sand in the home of an avid surfer.
When it comes to examining fibers as criminal evidence, there are eight different factors
that contribute to the significance of that evidence: 1) fiber type; 2) fiber color; 3)
number of fibers found; 4) location of the fiber; 5) fabric type; 6)multiple fiber
associations; 7) nature of contact; and 8) fiber transfer and persistence.
Volume of Fiber Production
Although billions of pounds of fibers are annually manufactured in the U.S. alone, and
although various textiles are produced using the same fiber types and color, the ability to
trace a single strand of fiber to a single manufacturer is not impossible. This is because of
the near improbability that two manufacturers could ever duplicate every single aspect of
the textile in question. Nonetheless, to avoid drawing false conclusions, a fiber examiner
must be extremely cautious when calculating the probability that a questioned fiber and
known fiber share the same originating source.
Analysis
Forensic fiber examiners carefully collect, prepare, and analyze samples using the
methods most appropriate for the given situation. Errors must be avoided every step of
the way.
Physical Matches
Sometimes cut, torn, or damaged pieces of fabric can be reconstructed so as to prove that
they were once a continuous piece. In instances like this, it is recommended that the
evidence be photographed as documentation.
Laboratory results are documented and reported in a uniform manner that is clear and
accurate.
Microscopy guidelines
Known and questioned fiber samples are compared point by point and side-by-side under
microscopes to determine if they fibers originated from the same source. The evidence is
first inspected visually and then either removed with tweezers, lifeted with tape, or gently
scraped into something uncontaminated such as plastic sheets or microscope slides.
Analysis
Fibers are first examined with a stereomicroscope in order for the examiner to document
its physical features such as crimp, length, color, diameter, luster, apparent cross section,
damage, and adhering debris. The fibers are then categorized as synthetic, natural, or
inorganic. If the known and questioned samples appear to be identical under the
stereoscope, the fibers are then compared and photographed side-by-side and point-bypoint under a comparison microscope, A comparison microscope is two microscopes
joined together so the questioned sample and known sample can bee examined
simultaneously.
Examining the physical characteristics of manufactured, natural, and inorganic
fibers
Manufactured fibers are described according to the diameter of the fiber, the color
variations and methods of dyeing the fiber, delustrant particles, the shape of the cross
sections, and the characteristics of the fiber’s surface. Additional characteristics must be
documented when examining natural fibers such as animal hair or plant fibers. The parts
of animal hairs that are examined include the root, medulla, cortex, and cuticles. The
structures within plant fibers that are studied include the epidermal tissue and crystals
(found in sacks, mats, and ropes), and the individual cell walls of which fabric and paper
are comprised.
Inorganic fibers such as asbestos minerals are examined using polar light microscopes
and scanning electron microscopes (SEM). Characteristics such as the refractive index or
elemental properties of inorganic fibers are also considered.
All fibers are also examined for th3e way in which they interact with light. Their reaction
to heat and solvents is also noted. The morphology of the fiber surface is also examined
with the use of a special scanning electron microscope. The samples used with scanning
electron microscopes are often coated with a conductive material such as gold to prevent
negatively charging the fiber sample with electrons.
Documenting the Report
The forensic fiber examiner documents the results in a written report. If the questioned
and known fibers display the same characteristics at the microscopic level, there is said to
be a positive association; the fibers are consistent with originating from the same source.
If it is determined that the known and questioned fibers are different from one other, they
are said to have a negative association, consistent with originating from two different
sources. Sometimes the forensic examiners are unable to come to a conclusion. An
inconclusive association occurs when no definitive conclusion can be drawn from the
comparisons. In that case, the forensic examiners must provide an explanation for why
the results proved to be inconclusive.
For more information on fiber analysis guidelines
http://www.fbi.gov/hq/lab/fsc/backissu/april1999/houckch1.htm#4.0.SummaryofFiberAn
alysisGuidelines
extensive, detailed information
24. TRACE EVIDENCE AND THE SIGNIFICANCE OF FIBER
Objective
Students should be able to describe how small pieces of fiber can be used as “trace
evidence” at the scene of a crime.
National Science Content Standard F: Science and technology in society
Rationale
One of the purposes of lectures or direct instruction is to disseminate information that
does not require higher cognitive thinking. The direct instruction in this lesson will give
the students the background knowledge they need when later they engage in activities
requiring higher order thinking skills. To help students organize the major points of the
lecture, it is recommended that teachers provide the students with outlines or written
accounts of the key ideas.
Materials
Lecture notes or outlines (recommended)
Hook and Focus:
Teacher: “Yesterday you were able to see and compare the difference between natural
and synthetic fibers when you examined them under the Phenom scanning electron
microscope. The ability to distinguish between microscopic pieces of fiber like that is
critical to the forensic scientist. Small pieces of fiber, when used as “trace evidence,” can
contribute significantly to the defense or conviction of a suspect. But there’s more to the
process ‘than meets the eye.’ In today’s lesson you’ll begin to see and appreciate the
complexities of fiber analysis.”
Background information
Trace Evidence:
1.
Everywhere we go, we leave a part of our physical selves behind. What we
leave behind could, if necessary, be used as “trace evidence.”
2.
2/8/10 Criminals do not understand this concept because most “trace evidence” is
microscopic, and not visible to the naked eye.
Page 96 Hair, Fiber and the Fabulous Phenom: An Introduction to Forensics
3.
It is impossible for anyone (including criminals) to remove all of their trace
evidence.
4.
Investigators looking for trace evidence look for anything that appears foreign
to the environment and that might be valuable as evidence.
5.
The smaller the trace evidence, the longer it persists at the scene of a crime.
Particles with irregular surfaces, such as broken glass or wool, persist longer
too. Investigators always photograph a crime scene first before collecting the
trace evidence.
6.
Methods for collecting trace evidence include a) shaking the item into a
container; b) brushing the evidence with a new toothbrush or paintbrush; c)
vacuuming; d) swabbing and hand-picking; e) using a solvent for oil or
grease; f) using adhesive tape when picking up fibers and hairs.
7.
Some particles can only be detected in sophisticated science laboratories with
high-powered microscopes [See the I-Search topic list for a listing of
microscopes used in crime scene investigations]
Fibers
1. Fiber is one kind of trace evidence that is usually collected from objects made of
cloth, including carpet, clothes, furniture, beds, and blankets.
2. When there has been contact from person-to-person, we say a “cross-transfer” of
fiber has occurred.
3. A fiber is the smallest portion of textile material. Fibers can be spun with other
fibers to create a “yarn.” When the yarn is woven or knitted together, it forms
fabric. Fabrics that are woven or knitted together can form “textiles.”
4.
There are over 1,000 known fibers and several thousand known dye formulas. All
manufactured dye formulas have been registered in a common database. This is
fortunate for those who must analyze the exact color and composition of the dye,
a painstakingly tedious job!
5. Fibers are first categorized as synthetic or natural. Synthetic fibers are man-made.
They include nylon, rayon, polyester.
6. Natural fibers come from plants and animals, and are used to make fabric. They
include cotton, wool, flax, jute, hemp, kapok.
(Pause for students to identify the type of fabric they are wearing.)
7. All fibers are much longer than their diameter. To identify a fiber, the experts
consider the origin of the materials within the fiber and how the fiber was woven
together to form the particular fabric.
8. Natural fibers refract light differently, depending on the fiber. Some can appear
brighter either along the edges and some appear brighter within the middle of the
fiber. Natural fibers usually appear circular when examined as a cross-section.
9. The color of a natural fiber is determined using a microspectrophotometer. [This
might be good time for the teacher to encourage students to use their
understanding of Greek and Latin roots to determine the meaning of multisyllabic
words such as this.] Colors in natural fibers are also determined using thin-layer
chromatography, a technique that separates the dye into its various components.
10. Synthetic fibers, unlike the circular structure of natural fibers, come in a variety of
shapes. The chemical makeup of synthetic fiber can be determined by infra-red
spectroscopy.
11. To determine the significance of a fiber at the scene of a murder, forensic
investigators analyze the fibers on both the suspect’s body and the victim’s body.
Fiber is considered “significant” if it is found both on the suspect’s body and the
victim’s body, but nowhere else.
12. If the fibers on a suspect and victim match in fiber type, color, and dye, forensic
scientists consider the match significant, especially because there are practically
an unlimited number of possible dye combinations for any single strand of fiber.
After providing the above foundation information, students might do a web search to
further investigate the topic “trace evidence” or “forensic fiber analysis.”
Assessment idea
“3-2-1”: Students write three things they learned, two things that surprised them, and one
question they still have about trace evidence and the significance of fiber.
For more information on fiber as trace evidence
http://www.apsu.edu/oconnort/3210/3210lect03.htm
trace evidence: fiber
http://www.enotes.com/forensic-science/trace-evidence
information on trace evidence
http://www.enotes.com/forensic-science/fibers
information on fibers
various fibers
25. LOCARD’S PRINCIPLE OF EXCHANGE
Objective
Upon completion of this hands-on simulation, students will explain the significance of
Locard’s Principle of Exchange to the field of forensic science.
National Science Teaching Standards A: Teachers select teaching and assessment
strategies that support the development of student understanding and nurture a
community of science learners.
Rationale
Research on brain-based classrooms indicates students are more likely to remember what
they learn when they engage with the content on a level that activates the emotions.
Because experiential, “hands-on” activities engage the emotional centers of the brain,
students are more likely to understand and remember the concepts they encounter while
they are engaged with the activity. In this hands-on simulation, students actively
experience (and remember) Locard’s Principle of Exchange, the guiding principle
fundamental to the science of forensics.
Materials needed
white T-shirt (brand new or freshly washed and air-dried)
single colored sweater
paper bag
tweezers
paper envelope
permanent black marker
clear sticky tape
microscope slides
light corn syrup
paper cup
medicine dropper
cover slips
fiber database (from the “Create a database” lesson)
newspaper
magnifying glass
compound microscope
Hook and Focus
Teacher: “Listen as I read a quote written by one of the two men who pioneered the study
of forensic science. Then be ready to summarize the quote in your own words.”
Teacher reads: “’It is impossible for a criminal to act, especially considering the intensity
of a crime, without leaving traces of his presence.’”
The teacher asks students to paraphrase the quote in writing and allows for a brief
discussion.
After a few students share their paraphrase of the Locard quote, explain the purpose of
this lesson: to test the principle that “every contact leaves a trace” of one’s presence.
Procedure
Before engaging in the simulation, the teacher provides background information
regarding Locard’s Exchange Principle.
Below is a brief summary:
Two Frenchmen pioneered the field of forensics: Alexandre Lacassagne and his student,
Edmond Locard. During World War I Locard made the now famous observation that no
criminal can act without leaving a trace of his presence. The fact that “every contact
leaves a trace” is now known as Locard’s Exchange Principle, the foundation upon which
forensics is built. In this activity that principle will be tested.
Directions for the simulation
Students work in pairs.
1. Student “A” puts on a clean white T-shirt.
Note regarding the T-shirts: The white T-shirts should either be new or freshly
washed, air dried or dried separately in a dryer. The point is that the T-shirts have no
fibers or hairs on them at the start of the lesson. There are a few ways to handle this: 1)
Purchase very cheap new white tee shirts, leaving them in the wrapping until the start of
the activity, or 2) Let the students come prepared with a freshly-washed T-shirt that has
been air-dried or dried in the dryer alone and then transported to class in a clean paper
bag.
2. Student “B” watches her/his partner carefully, recording in a science journal the places
and activities Student A engages in for a period of time.
Note: Depending on the nature of the school day or period, students might go about their
normal activities for a few hours or you might engage the students in a variety of
activities during a given amount of time. This activity works best if the students can
engage in a wide variety of activities that requires them to move on the floor, on the
school yard, etc., so that they are coming into contact with a wide variety of surfaces. A
game or activity that results in appropriate physical contact works also, so that the hairs
or fibers from one student might land on another. All the while the students are
interacting, Student B should be carefully recording what Student A is doing and where
the activity is occurring.
3. After the period of activity is over, Student A removes the white T-shirt and places it
in a paper “evidence” bag.
4. Collect the known (K) fiber samples from each activity location. Use the collecting
techniques employed by forensic examiners, such as using tweezers or clear sticky tape.
Remember to label all collected samples.
5. Using tweezers, remove all fibers from the collection envelope.
6. Make a permanent mount (for the optical microscope) and sample stub (for use with
the Phenom) for each known fiber type.
7. Students record each sample in their notebooks as K-1, K-2, etc.
8. Students open the evidence bag containing the T-shirt, and carefully place the T-shirt
on a sheet of newspaper.
9. Using magnifying lens, students scan the area of the T-shirt, using tweezers or clear
sticky tape to pick up any hair or fibers. Students label the collected samples form the Tshirt as Q-1, Q-2, etc. Be sure to examine both sides of the T-shirt.
10. Examine the fiber evidence with a magnifying glass, microscope, and Phenom table
top SEM.
11. Identify and describe the (K) fibers from each location.
12. Identify and describe the (Q) fibers collected from the T-shirt.
13. For each recovered (Q) fiber, see if it matches a (K) fiber. A match indicates both (Q)
and (K) fibers appear to have similar characteristics.
14. Write up your comments and results in your science notebook. (See attachment for
sample fiber comparison.
15. Students conduct further research into the pioneering work of Edmond Locard and
Alexandre Lacassagne.
Assessment: Students write an essay or research report describing the significance of
Locard’s Principle of Exchange to the field of forensics.
Sample Fiber Comparison
Q
Exhibit
Number
(Recovered,
Unknown
Source)
1
3
7
Comments
Fiber Type: cat hair
Fiber diameter 19 µm
Medulla width: 10µm
Medullary index: 0.52
Medulla type: uniserialladder
Scale type: spinous
Color: white
Unusual characteristics: no
ovoid bodies
Fiber Type: human hair
Medulla type: continuous
Scale type: imbricate
Color: brown
Unusual characteristics:
brown pigment granules
Fiber Type: synthetic
Medulla width: n/a
Medullary index: n/a
Medulla type: n/a
Scale type: n/a
Color: blue
solid fiber; no holes
K
(Known
Fiber
And
Source)
1
cat hair –
Biff’s
backpack
2
Alisha’s
shirt
3
sofa in
library
Comments
Fiber Type: cat hair
Medulla type: uniserialladder
Scale type: spinous
Color: white
Unusual characteristics: no
ovoid bodies
Fiber Type: human hair
Medulla type: continuous
Scale type: imbricate
Color: brown
brown pigment granules
Fiber Type: synthetic
Medulla width: n/a
Medullary index: n/a
Medulla type: n/a
Scale type: n/a
Color: blue
solid fiber; no holes
Source: Rainis, K.G. (2006). Hair, Clothing, and tire track evidence: Crime-solving science experiments.
Berkeley Heights, NJ: Enslow Publishers.
For more information on Locard’s Principle of Exchange
http://www.enotes.com/forensic-science/locard-s-exchange-principle
Locard’s exchange principle
http://library.thinkquest.org/04oct/00206/tte_every_criminal_leaves_a_trace.htm
Paragraph about trace evidence included.
trace evidence
http://www.profiling.org/journal/vol1_no1/jbp_ed_january2000_1-1.html
heady essay explaining the importance of Evidence Dynamics, influences that affect
physical evidence
http://www.fbi.gov/hq/lab/fsc/backissu/oct1999/trace.htm
trace evidence recovery guidelines from the FBI website
Rainis, K.G. (2006). Hair, Clothing, and tire track evidence: Crime-solving science
experiments. Berkeley Heights, NJ: Enslow Publishers.
26. PROBABILITY
Objective
Students identify the ways in which the laws of probability are used in forensic analysis.
National Science Program Standard C: The science program should be coordinated
with the mathematics program to enhance student understanding of mathematics in the
study of science and to improve student understanding of mathematics.
Rationale
The evidential value of trace fibers and hairs relies upon the laws of probability and
statistics. Students, if not in their own research, will certainly encounter discussions of
probability and statistics in the articles they read pertaining to forensic fiber analysis.
Below are a few “big ideas” related to probability theory. The teacher will find lesson
plan ideas in the list of websites provided.
1. The probability of a future event occurring can be placed along a continuum from
impossible to certain. By definition, probability is a measure of the likelihood of
an event occurring.
2. The probability of an event occurring can be written as a number between 0 and
1, with 0 representing impossibility and 1 representing certainty. For example, ½
indicates there is an even chance of the event occurring.
3. Experimental probability, the relative frequency of outcomes of an event, can be
used as an estimate of the exact probability of the event. The experimental
probability of an event is generated through the collection of data. The law of
large numbers says that the greater number of trials conducted, the better the
estimate will be.
4. Sometimes the exact probability of an event can be calculated by analyzing the
event itself in a manner called theoretical probability. The formula for conducting
the theoretical probability of an event is
number of outcomes in the event
number of possible outcomes
The probability of an event occurring can be written as a ratio called relative
frequency. The relative frequency of an event is
number of observed occurrences of the event
total number of trials
5. A simulation is a technique used for answering real-world questions or making
decisions in which an element of chance is involved. To see what could likely
occur in the real event, a model must be designed with the sample probabilities of
the real situation.
6. The sample space for an experiment or chance situation is the set of all possible
outcomes for that situation or experiment. In a deck of cards, for example, the
sample space consists of all 52 playing cards. An event is a subset of the sample
space. The event of drawing a Queen has four elements or outcomes in the sample
space (because there are four Queens in a deck of playing cards).
7. An independent event has no effect on another (such as in the rolling of dice:
Because I got rolled a “6” this time does not affect the roll of the dice next time).
8. When the probability of an event depends on the result of the first event we say
that event is dependent. For example, the likelihood that I will draw a Queen from
a stack of playing cards depends on how many and which cards have already been
drawn from the stack.
Resources and information related to probability
http://mathforum.org/library/topics/probability
links to hundreds of articles, lessons and applets related to probability
http://nlvm.usu.edu/en/nav/frames_asid_146_g_3_t_5.html
create a box model of up to 16 cubes that can be drawn at random and replaced. Results
are displayed as a bar graph and compared to the theoretical results
“toss” a coin; results displayed as bar graph
www.shodor.org/interactivate/activities/prob/index.html
create a spinner or two dice
http://www.urj.ucf.edu/vol1issue1/russo/index.php
undergraduate thesis discussing the forensic investigation of fibers. New techniques
reduce the chance of incidental matches.
general article about hair as trace evidence; the last paragraph refers to probability
http://peacesecurity.suite101.com/article.cfm/forensic_hair_analysis_faulty#ixzz0XoF55t
QX
article about the dangers of hair analysis to convict a suspect; the probability of finding a
false match is greater than it was once thought to be.
article on fibers and probability theory; links to several more articles about fiber analysis
Van de Walle, J. A. (2007). Elementary and middle school mathematics: Teaching
developmentally. Boston: Pearson.
A good source for teachers of middle school and/or those high school students who
need a conceptual understanding of mathematics.
27. WRITING CLEAR LAB REPORTS
Objective: Students write clear, concise forensic lab reports.
explanations.
Rationale: The ability to communicate the results and conclusions of any research
project or investigation is an essential skill developed across the curriculum. Likewise,
the ability to write complete, well-organized technical reports is an essential skill for
scientists of all specialties. Students learn to integrate literacy skills with science content
when writing clear, concise, and accurate forensic reports.
Procedure
The standard format for writing lab reports is outlined below. How and when you present
the components of the report will depend on the structure of your class and the readiness
of your students.
1. Title Page
• The title of the investigation
• The name of the student-investigator(s)
• Date
2. Title of Investigation
3. Introduction / Purpose
• Write a paragraph explaining the purpose of the investigation, how the
investigation was carried out, the findings of the investigation, and the
conclusion.
4. Materials
• List everything used during the investigation
5. Methods
• Describe the procedure taken to complete the investigation. It should be
detailed enough that another investigator could replicate your procedures.
Include diagrams if necessary.
6. Data
• Include numerical and descriptive (not interpretative) data.
7. Results and Discussion/Analysis
• This is where the investigator interprets the data to determine whether or not
the unknown hair or fiber (Q) seems to match the known (K) hairs or fibers.
This is also where you discuss any challenges you encountered during the
investigation or any mistakes you might have made while conducting the
investigation.
8. Conclusion
• Here is where you determine whether or not the hair or fiber in question
matches the known hairs or fiber. Remember, hair and fiber is never used as
the sole source of evidence to prove a suspect’s guilt or innocence. Therefore,
choose your words carefully when drawing conclusions. Sample wording is
attached to this handout. In addition, you will need to make either a positive,
negative, or inconclusive association based upon your results:
a. Positive associations are made between the known and questioned
fibers when the fibers exhibit the same microscopic characteristics and
optical properties in all tested parameters, and are therefore consistent
with originating from the same source.
b. Negative associations are made when the Q and K fibers are different
in some significant aspect, and therefore originate from separate
sources.
c. Inconclusive results occur when no conclusion can be reached.
Forensic examiners must always provide an explanation as to why a
definitive conclusion was not possible.
9. Figures, Graphs, Photos, Illustrations
• The recommended method for documenting hair and fiber analysis is
photography, a method easily accessible when capturing images from the
Phenom. Remember that all visuals must be labeled with a descriptive title.
10. References
• Any facts that require documentation or any outside research that informed
your work should be listed in the reference section.
Sample language for writing conclusions
1. The questioned hair exhibits the same microscopic characteristics as the hairs in the
known hair sample and, accordingly, is consistent with originating from the source of the
known hairs.
2. The questioned hair is microscopically dissimilar to the hairs found in the known hair
sample and, accordingly, cannot be associated to the source of the known hairs.
3. Similarities and slight differences were observed between the questioned hair and hairs
in the known hair sample. Accordingly, no conclusion could be reached as to whether the
questioned hair originated from the same source as the known hairs.
4. “No synthetic or plant fibers were recovered. Four out of the six recovered hairs are
animal (horse, beaver, dog, and muskrat). Two human hairs were recovered: black and
brown. The recovered human black hair has a continuous medullary core. This fact,
alone, is not enough to suggest that the detained individual was connected with the
assault. [It is suggested that] the district attorney have this individual’s coat carefully
examined for fiber evidence. Since the victim was a taxidermist, the recovery of unusual
animal fibers from the scene that are consistent with the recovered evidence, and/or blond
hairs, would add great weight to placing that individual at the scene” (Rainis, 2006,
p.114).
5. “All exhibits are natural fibers. Exhibits #1 and #4 are deer hair. Exhibit #2 is cattle
hair – consistent with blood analysis results. Exhibit # 3 is cat hair and Exhibit #5 is horse
hair. Exhibit #6 is rabbit hair. See the Evidence Information Table (Table 6). Trace
evidence confirms the presence of a deer carcass in the bed of the suspect’s truck.
However, there is no evidence to support when the deer hairs were deposited. The
landowner cannot be issued a summons based solely on the fiber evidence developed in
this case” (Rainis, 2006, p. 116).
6. Based on the fiber evidence, the suspect can be forensically linked to the jewelry store.
7. …comparison of samples from K and Q sources determine that they are consistent
with having originated from the same source.
For more information on forensic lab reports
http://www.icaew.com/index.cfm/route/165215/icaew_ga/en/Special_interest_groups/For
ensic/An_introduction_to_forensic_report_writing_skills
an introduction to forensic report-writing skills
http://www.scribd.com/doc/14488082/Writing-a-Computer-Forensic-Technical-ReportBy-Mark-Maher
offers a methodology for writing easy-to-read, well-organized forensic reports
http://www.independent.co.uk/news/bloody-sunday-forensic-report-fatally-flawed1119494.html
Newspaper article from Britain, 1999
28. THE CSI EFFECT
Objective
Students identify and summarize discrepancies between real-world forensic science and
television portrayals of crime scene investigations.
National Science Content Standard F: Science and technology in society.
Rationale
Critical thinking in the science classroom builds upon some of the same habits of mind
developed in other content areas such as Social Studies or Language Arts: Students are
taught to gather and think logically about data or information they collect, to critically
analyze the hypotheses they develop, and to effectively communicate the results of their
investigations or research. In this reading activity, students use research skills to
investigate and critically analyze the effect popular television shows have had on the
population’s real-world expectations of crime scene investigations.
Hook and Focus
Teacher: “For as long as television has been around, criminal and detective dramas have
been favorites among viewers. What are some of the detective or criminal dramas, past
and present, that you are familiar with? (Allow student input)… Most of you have
probably seen at least a few episodes of one or more of those programs. You therefore
have some idea of what you think the process of forensic science looks like. But as we
will see from the research, not only do the television investigations differ from real-life
investigations, but what the public sees on television can actually have a negative effect
on what happens in real-world forensic labs and courtrooms. This phenomenon – the
skewed public perception of what forensic science is all about – is called “The CSI
Effect.”
Procedure
1. In small groups students discuss their perceptions of criminal investigations as
based upon certain television shows such as the “CSI” series.
2. Teacher models how to paraphrase and summarize reading material.
a. The process involves rewording the text’s meaning.
b. Representing the meaning of the text in a new form, such as a table or
graph, is also acceptable.
c. Encourage use of tools such as dictionaries and thesauruses.
3. Teacher issues or assigns article(s) related to the CSI Effect.
4. Students read and practice paraphrasing or summarizing the contents of the
article.
Assessment: Students summarize documented discrepancies between real-world
forensics and television portrayals of crime scene investigations.
Strong summaries exhibit the following characteristics:
• Language is accurate and clear
• Language is concise
• Only main ideas and essential supporting details are included in the summary
• Nonessential material, such as illustrative material and statements of elaboration,
have been eliminated in the summary
• Trivial and redundant material has been eliminated
For more information on the CSI Effect
http://www.enotes.com/forensic-science/television-shows
television shows contributing to the CSI Effect
http://www.all-about-forensic-science.com/csi-effect.html
a different perspective of the CSI Effect
http://www.youtube.com/watch?v=FaJC3oXIDCA&feature=related
interview with Judith Fordham, author of “Life, law, and Not Enough Shoes” Discusses
how unrealistic some parts of CSI are… (poor sound quality)
http://www.youtube.com/watch?v=YfHkpM7gXjk
CSI clip featuring the Phenom SEM
http://forensicscience.suite101.com/article.cfm/investigating_the_csi_effect
brief, general overview of the CSI Effect
29. CLOSURE
Objective
Students express what they have learned about hair, fiber, and forensic science.
National Science Teaching Standard A: Teachers of science plan an inquiry-based
science program for their students. In doing this, teachers select teaching and assessment
strategies that support the development of student understanding and nurture a
community of science learners.
Rationale
In the KWL activity conducted at the start of the unit, students shared what they wanted
to learn about the topic of hair, fiber and forensic science. To bring a satisfying closure to
their investigations (and to reinforce the concepts learned), students reflect on everything
they have learned related to the topic.
Materials
The original KWL chart developed in the first lesson, “Assessment of Prior Knowledge.”
Procedure
1. Review with the students the questions they asked at the start of the unit. These are the
questions found in the “K” (What we want to know”) column.
2. In small groups, students discuss what they have learned from the unit.
3. Bring the class together to share what they have learned from the unit.
3. In the “L” column (“What we learned”) write the answers the students found during
the course of study.
3. Some questions might still be left unresolved. If you have not yet finished the unit,
some students might volunteer or be assigned an investigation of the answer. Otherwise,
you might add a fourth column: “Questions we still have.”
4.Additional forms of assessment might include:
•
•
•
•
•
•
•
•
•
•
•
•
•
Journal notes
Written reports
Diagrams
Models
Poster session
Speech
Lead a discussion
Paint; sculpt; play an instrument; sing
Outline
Power Point
Video
Educational game
Teacher-made examination
Visuals of hair from <www.fbi.gov>
structure of hair
SEM photomicrograph
of scales on hair
human scale pattern
uniserial ladder medulla
Multiserial ladder medulla
ovoid bodies in dog hair
human hair root
Caucasian ancestry hair
cross section
Caucasian ancestry
head hair
African ancestry
head hair
Asian ancestry
head hair
31. REFERENCES IN THE ORDER PRESENTED
For a little more introductory information
http://wiki.nsdl.org/index.php/MiddleSchoolPortal/Forensic_Science
justification for teaching forensic science in middle school
http://www.phenomworld.com/applications/education.php#http://hwcdn.net/b3d9w2e7/cds/phenom/FEI_NC
SU_Classroom_Instruction_F8_Medium.flv
video showing the value of using the Phenom in hair and fiber analysis
1. For more information on working with second language learners
Cary, S. (2000). Working with Second Language Learners: Answers to Teachers’ Top
Ten Questions. Portsmouth. NH: Heinemann.
Larsen-Freeman, D. (2008). Techniques and principles in language teaching (2nd ed.).
Oxford University Press.
2. For more information on the KWL strategy
http://olc.spsd.sk.ca/DE/PD/instr/strats/kwl/
brief explanation of the KWL strategy
http://www.indiana.edu/~l517/KWL.htm
clear explanation of purpose and procedure for the KWL. Includes example
https://www.msu.edu/course/cep/886/Reading%20Comprehension/7Learn_Serv_Proj_K
WL.html
very simple outline of the KWL strategy, applied to reading
2. For more information on forensic science
http://www.youtube.com/watch?v=ekTbRJbN6is
quick overview of forensic scientists
http://www.all-about-forensic-science.com/
lots of information
http://www.aafs.org/yfsf/index.htm
young forensic science forum
Forensic science resources for the beginner
Cooper, C. (2008). Eyewitness: Forensic science. London: DK Publishing.
Pentland, P., & Stoyles, P. (2003). Science and Scientists: Forensic Science. Broomall,
PA: Chelsea House Publishers.
Sheely, R. (1993). Police lab: Using science to solve crimes. New York: Silver Moon
Press.
Yeatts, T. (2001). Forensics: Solving the crime. Minneapolis: The Oliver Press, Inc.
Yount, L. (2007). Forensic science: From fibers to fingerprints. New York: Chelsea
House Publishers.
5. For more student-friendly information on the Phenom in general
http://www.youtube.com/watch?v=n3Xngnnv47w&NR=1
YouTube: Youngsters using the Phenom
http://www.youtube.com/watch?v=YfHkpM7gXjk&NR=1
YouTube: Phenom featured on CSI NY
http://www.youtube.com/watch?v=Rk7jGgMlPek&feature=related
YouTube: FEI promo of the Phenom
http://www.phenomworld.com/applications/education.php#http://hwcdn.net/b3d9w2e7/cds/phenom/FEI_Hea
lth_and_Science_School_Fl8Medium.flv
high school students describe the value of the Phenom SEM
6. For more information on the scanning electron microscope
http://www.5min.com/Video/Scanning-and-Transmission-Electron-Microscopes150625001
five minute, clear explanation of SEMs and STEMs.
FEI website
http://www.fei.com/uploadedFiles/Documents/Content/2006_06_AllYouWanted_pb.pdf
produced by FEI; includes dynamic visuals
http://www.mse.iastate.edu/microscopy/home.html
includes age-appropriate descriptions and diagrams of the SEM for elementary, high
school, and college level students.
http://school.discoveryeducation.com/lessonplans/activities/electronmicroscope/
includes ‘how a SEM works’ within the body of the procedure
http://www.jsu.edu/depart/biology/learning_about_microscopy.html#thelightmicro
includes a paragraph which sums up how a SEM works. Appropriate for more
experienced readers.
http://www.coe.uh.edu/archive/science/science_graphics/sciencegr2.html
compound microscope
http://www.unl.edu/CMRAcfem/semout.htm
SEM images
http://micro.magnet.fsu.edu/primer/index.html
good for learning the vocabulary in context for microscopy
http://www.youtube.com/watch?v=fToTFjwUc5M
YouTube: The structure and function of the scanning electron microscope
http://www.lessonplanet.com/directory/Science/Biology/Microscopes/Scanning_Electron
_Microscopes
lesson plans for scanning electron microscopes
For more information on forensics and the scanning electron microscope
http://www.enotes.com/forensic-science/scanning-electron-microscopy
SEM and forensics
http://www.enotes.com/forensic-science/microscopes
SEM and forensics
http://www.enotes.com/forensic-science/inorganic-compounds
SEM and forensics
http://www.enotes.com/forensic-science/search?m=cs&url=forensic-science&q=SEM
includes a bit on how the SEM is used with forensics
http://www.mse.iastate.edu/microscopy/vacuum2.html
diagrams and explanations for different grade levels
http://www.youtube.com/watch?v=OxlAUFqIiqA&feature=related
SEM and forensics
http://www.youtube.com/watch?v=qrUzfUcMtaA&NR=1
SEM and forensics
Cynthia Villwock from Chemeketa Community College in Salem, Oregon, has used the
Phenom with a mini CSI unit she developed for high school students.
cynthia.villwock@chemeketa.edu
8. For more information on size and scale
http://www.youtube.com/watch?v=FXZwi7Lf9Yw&feature=channel
explains how small a nanometer is. Quick video.
http://www.youtube.com/watch?v=1Nl87_pqOZ4&feature=related
brief. gives analogies for the size of a nanometer
http://www.magnetmail.net/Actions/email_web_version.cfm?publish=newsletter&user_i
d=NSTA&message_id=627591
magnitude and scale links for elementary level students. NSTA
http://www.nisenet.org/viz_lab_image_scaler
image scaler from human to nano
http://www.youtube.com/watch?v=8BTGzVScBso&feature=channel_page
entertaining introduction to nanotechnology, produced by OMSI
Rob Sleezer has developed a middle school lesson that teaches size and scale using the
Phenom scanning electron microscope. rzleezer@uark.edu
8. For information related to nanotechnology
http://science.howstuffworks.com/nanotechnology.htm
good visuals – related to nanotechnology
from FEI’s website. This links to several related websites for nanotechnology
http://www.youtube.com/watch?v=Cm90Md81zZQ&NR=1
Intro to nanotechnology. Narrated by Alan Alda.
http://www.youtube.com/watch?v=gYR8lV23Pow&feature=fvw
Nanotechnology. 9 minutes
http://www.youtube.com/watch?v=S4CjZ-OkGDs
10 ½ minutes explaining nanotechnology
http://www.nisenet.org/
links to sites and information on nanotechnology
9. For more information on creating a reference collection of hair and fiber
(This was the original source of this lesson)
http://www.alittlecreation.com/alliance/lesson2.html
a lesson on collecting hair and fur
10. For more information on preparing samples for the Phenom:
Phenom User Manual produced by FEI company 2008
5350 NE Dawson Creek Drive Hillsboro, OR 97124
http://www.fei.com/uploadedFiles/Documents/Content/2008_05_PhenomSamplePreparat
ion.pdf
the original sample preparation guide for the Phenom
http://www.phenom-world.com/productinformation/phenom.php#http://hwcdn.net/b3d9w2e7/cds/phenom/FEI_tv_SamplePrep.fl
v
Watch a video showing proper sample preparation.
http://www.phenom-world.com/product-information/phenom.php#movies
links to other videos featuring the Phenom
http://www.phenom-world.com/productinformation/phenom.php#http://hwcdn.net/b3d9w2e7/cds/phenom/sample-charging.flv
an explanation of “sample charging”
11. For more information on hair analysis
This is the original lesson source. Includes a simulation on blood analysis.
http://www.ehow.com/about_5445024_importance-hair-evidence-forensics.html
general overview of how hair is used as forensic evidence. Easy reading.
“caught by a hair” story from real life
12. For more information on hair
A detailed manual and guide for the study of human hair. Complete with attractive
http://www.fbi.gov/hq/lab/fsc/backissu/july2004/research/2004_03_research02.htm
A detailed manual and guide for the study of animal hair. Complete with attractive
http://sciencespot.net/Media/FrnsScience/Hairsfibers08.ppt#256,1,Slide 1
PowerPoint lesson complete with photos and diagrams of hairs and fibers
http://sciencespot.net/Media/FrnsScience/hairfibernotewkst.pdf
student worksheets for the above Sciencespot site
http://sciencespot.net/Media/FrnsScience/hairfiber_IDlabwkst.pdf
simple worksheet for analyzing hair
http://sciencespot.net/Media/FrnsScience/hairfiberchallenge.pdf
photos of hair and fiber prepared as a worksheet for students to guess their origin.
hair and microscopy
hair as evidence
http://sciencespot.net/Pages/classforsci.html#hairsfibers
PowerPoint of hair information
trace evidence and hair
http://www.time.com/time/health/article/0,8599,1720520,00.html
TIME magazine article on hair and forensics
http://www.mediacy.com/index.aspx?page=AS_123
hair: old vs. new cut
http://www.microscopy-uk.org.uk/mag/artnov04macro/tchair.html
hair as seen through a fiber optics illumination system
http://www.chem.sc.edu/analytical/chem107/lab4_032205.pdf
diagrams and photomicrographs with lecture notes. Original source comes from the
fbi.gov website below
The original source of diagrams and photomicrographs seen in several sites and books.
Article by Deedricks, posted on www.fbi.gov website
hair analysis article
13. For more information on the Jigsaw activity
http://www.jigsaw.org/overview.htm
jigsaw
http://olc.spsd.sk.ca/DE/PD/instr/strats/jigsaw/
jigsaw
Cooper, J.M. (ed.). (2003). Classroom teaching skills (7th ed.). Boston: Houghton Mifflin.
For more information on tools used in the analysis of trace evidence
15. For more information on topics students might choose to research
http://csidegrees.com/jump/crime-scene
investigation/index.php?s=msn&k=forensic%20science%20degree&ss=fmuonlineuoponline&c=campaignname
includes pay information
instruments and tools used in the analysis of trace evidence
http://csidegrees.com/jump/crime-scene-investigation/index. php?s=msn&k=
forensic%20science%20degree&ss=fmuonline-uoponline&c=campaignname
includes degrees related to forensic science
jobs. Good link, although it doesn’t list the jobs straight out. More of a resource board.
http://www.forensicartist.com/links.html
lists several links to the topic of forensic art
http://www.forensicartist.com/
forensic art certification site
http://www.all-about-forensic-science.com/forensic-science-careers.html
careers in the forensic sciences. The little videos and photos are informative.
http://aafs.org/default.asp?section_id=resources&page_id=choosing_a_career#Bookmark
1
tells all about forensic science as a career. Lists resources – relevant organizations that
would be good for research.
http://dsc.discovery.com/videos/human-forensic-entomologist.html
Discovery clip on forensic entomologist. Interesting. Brief interview.
http://www.all-about-forensic-science.com/forensic-linguistics.html
fascinating re: linguistics and crime
http://english.forensischinstituut.nl/
Nederlands Forensisch Instituut.
http://www.crime-scene-investigator.net/JOB-08-10-05.html
Job description for Forensic Scientist I, Oregon State police
http://www.enotes.com/forensic-science/training
info on the training required to enter forensics
ACFEI
names a few specialist fields
http://www.youtube.com/watch?v=DsTsPWH-clo
advertises a course at Lancanshire, but good
http://www.youtube.com/watch?v=TDKf3KgeAPc&NR=1
attorneys and forensic experts – certified forensic consultant
somewhat boring, but might be of interest to kids interested in law/lawsuits
http://www.youtube.com/watch?v=kEkk13J3Ylk
brief explanation of how forensic scientists are in the lab whereas the investigators are on
the scene of the crime.
resource board for jobs related to forensic science.
16. For more information on analyzing and identifying unknown samples of hair
This is the original lesson source. It also includes a simulation on blood analysis.
16. For more information on forensic fiber examination
The notes on forensic fiber examination were taken verbatim from this website, although
some of the original content was omitted for the sake of brevity. Extensive information
found at this website.
19. For more information related to the medulla or the medullary index
background on hair as used in forensics; discusses the parts of hair
http://images.google.com/images?sourceid=navclient&rlz=1T4SUNA_en___US288&q=
medullary+index&um=1&ie=UTF8&ei=Cn4tS6_cLISusgP6s9DDBA&sa=X&oi=image_result_group&ct=title&resnum=4
&ved=0CBoQsAQwAw
photographic images of medulla (and other images related to other science topics)
http://images.google.com/imgres?imgurl=http://home.gwu.edu/~wfrowe/Jj02.jpg&imgref
url=http://home.gwu.edu/~wfrowe/cases_graphic.htm&usg=__XT2SGHr0SU25nk6xNm
UMppjf2ZM=&h=437&w=640&sz=37&hl=en&start=1&um=1&tbnid=AdUY8CseI_LtM:&tbnh=94&tbnw=137&prev=/images%3Fq%3Dmedullary%2Bindex%26hl%3De
n%26rlz%3D1T4SUNA_en___US288%26sa%3DX%26um%3D1
article using the medullary index in the context of a real situation
http://hypertextbook.com/facts/1999/BrianLey.shtml
discusses the diameter of a human hair
http://www.phenom-world.com/applications/education.php#
links to scale lesson using the Phenom
20. For more information on weave patterns
This was the source of the lesson idea.
20. For more information related to weave patterns and fabrics
http://en.wikipedia.org/wiki/Plain_weave
general introduction to plain weave type
http://www.fabrics.net/cotton.asp
glossary of cotton fabrics and weaves
http://en.wikipedia.org/wiki/Twill
information on twill
http://www.cyberfiberonline.com/glossaryG.html
extensive glossary
http://www.harisons.com.my/?id=38&mnu=38
extensive fabric glossary
Mainprize, V. (Editor). (1998). Craft workshop: Fabric. New York: Crabtree Publishing
Company.
Chapman, G., and Robson, P. (1995). Salvaged! Art from fabric with projects using rags,
old clothing and remnants. New York: Thomson Learning.
Fourneir, N., & Fountier, J. (1995). In sheep’s clothing: A handspinner’s guide to wool.
Loveland, CO: Interweave Press.
Jerstorp, K. & Kohlmark, E. (1988). The textile design book: Understanding and creating
patterns using texture, shape, and color. Asheville, NC: Lark Books.
21. For more information on the features of fiber
http://www.imageafter.com/image.php?image=b17maartent1480.jpg
photo of cotton
22. For more information on fiber analysis
http://www.authorstream.com/Presentation/danielharvey9-167032-forensics-fiberanalysis-entertainment-ppt-powerpoint/
forensic fiber analysis power point
http://www.imageafter.com/category.php?category=fabrics
royalty free photos of fabrics
http://www.imageafter.com/category.php?category=fur
royalty free photos of fur
various fibers
23. For more information on fiber analysis guidelines
http://www.fbi.gov/hq/lab/fsc/backissu/april1999/houckch1.htm#4.0.SummaryofFiberAn
alysisGuidelines
extensive, detailed information
24. For more information on fiber as trace evidence
http://www.apsu.edu/oconnort/3210/3210lect03.htm
trace evidence: fiber
http://www.enotes.com/forensic-science/trace-evidence
information on trace evidence
http://www.enotes.com/forensic-science/fibers
information on fibers
various fibers
25. For more information on Locard’s Principle of Exchange
http://www.enotes.com/forensic-science/locard-s-exchange-principle
Locard’s exchange principle
http://library.thinkquest.org/04oct/00206/tte_every_criminal_leaves_a_trace.htm
Paragraph about trace evidence included.
trace evidence
http://www.profiling.org/journal/vol1_no1/jbp_ed_january2000_1-1.html
heady essay explaining the importance of Evidence Dynamics, influences that affect
physical evidence
http://www.fbi.gov/hq/lab/fsc/backissu/oct1999/trace.htm
trace evidence recovery guidelines from the FBI website
general article about hair as trace evidence; the last paragraph refers probability
QX
article about the dangers of hair analysis to convict a suspect’ the probability of finding a
article on fibers and probability theory; links to several more articles about fiber analysis
Rainis, K.G. (2006). Hair, Clothing, and tire track evidence: Crime-solving science
experiments. Berkeley Heights, NJ: Enslow Publishers.
26. Resources and information related to probability
http://mathforum.org/library/topics/probability
links to hundreds of articles, lessons and applets related to probability
create a box model of up to 16 cubes that can be drawn at random and replaced. Results
are displayed as a bar graph and compared to the theoretical results
“toss” a coin; results displayed as bar graph
www.shodor.org/interactivate/activities/prob/index.html
create a spinner or two dice
general article about hair as trace evidence; the last paragraph refers to probability
QX
article about the dangers of hair analysis to convict a suspect; the probability of finding a
27. For more information on forensic lab reports
http://www.icaew.com/index.cfm/route/165215/icaew_ga/en/Special_interest_groups/For
ensic/An_introduction_to_forensic_report_writing_skills
an introduction to forensic report-writing skills
http://www.scribd.com/doc/14488082/Writing-a-Computer-Forensic-Technical-ReportBy-Mark-Maher
offers a methodology for writing easy-to-read, well-organized forensic reports
http://www.independent.co.uk/news/bloody-sunday-forensic-report-fatally-flawed1119494.html
Newspaper article from Britain, 1999
28. For more information on the CSI Effect
http://www.enotes.com/forensic-science/television-shows
television shows contributing to the CSI Effect
http://www.all-about-forensic-science.com/csi-effect.html
a different perspective of the CSI Effect
http://www.youtube.com/watch?v=FaJC3oXIDCA&feature=related
interview with Judith Fordham, author of “Life, law, and Not Enough Shoes” Discusses
how unrealistic some parts of CSI are… (poor sound quality)
http://www.youtube.com/watch?v=YfHkpM7gXjk
CSI clip featuring the Phenom SEM
http://forensicscience.suite101.com/article.cfm/investigating_the_csi_effect
brief, general overview of the CSI Effect
2/8/10 Page 138

Hair, Fiber, and the Fabulous Phenom

Transcription

Similar documents

SF]ELF F1 ELP

Andarko Petroleum: Pipeline Restoration

ORGANIC ROOT STIMULATOR Carrot Oil

Salon Product

Who is Arvig?

Girls Scrunchie

here - Women`s ROGAINE

Featured on Style Me Pretty - Black Tie at Goodstone Inn

Bridal Hair, Kenra Style

Dry Twist Out 101