Unit 4
Trace Evidence I:
Hairs and Fibers
CTE Forensics/Law &
Public Safety
1-2
Learning Standards and Objectives
CTE: 6.0 = Analyze Investigative Procedures (6.1 - 6.7); Science:
Strand 1 - Concept 1 PO 1 - 4; Concept 2 PO 1 - 5; Concept 4 PO
1 - 4; Strand 2 - Concept 1 PO 1 - 4; Strand 3 - Concept 2 PO 2;
Strand 4 - Concept 1 PO 1 - 5, Concept 2 PO 1 – 4; Strand 5 Concept 1 PO 1,2, & 4; Strand 6 - Concept 3 PO 9.
Students will be able To:
evaluate the use of the microscope for trace evidence and
hair/fibers. To distinguish the history, characteristics, physiology,
patterns, types, development & preservation; Continue to
evaluate trace evidence (glass, paint, soil) using a comparison
microscope; practicum exercise.
Measurements: : Quizzes, class discussions, comprehension
assessments, performance assessments (labs).
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Learning Objectives
Identify and Describe the hair cuticle, cortex and medulla
Describe the three phases of hair growth
Identify and Explain the distinction between animal and human hair
List hair features that are useful for the microscopic comparison of
human hairs
Explain the proper method of collection of hair evidence
Describe the role of DNA typing in hair comparisons
Classify fibers
Describe the structure of a polymer
List the properties of fibers that are most useful for forensic
comparisons
Describe the proper method of collection of fiber evidence
3
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Key Terms – Be prepared for a Quiz
Anagen phase
Monomer
Catagen phase
Natural Fibers
Cortex
Nuclear DNA
Cuticle
Polymer
Follicular tab
Telogen phase
Macromolecule
Manufactured fibers
Medulla
Mitochondrial DNA
Molecule
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Introduction
• Hair is encountered as physical evidence in a wide
variety of crimes.
• Although it is not yet possible to individualize a human
hair to any single head or body through its
morphology, it still has value as physical evidence.
• When properly collected and submitted to the
laboratory, accompanied by an adequate number
of standard/reference samples, hair can provide
strong corroborative evidence for placing an
individual at a crime scene.
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Morphology of Hair
• Hair is an appendage of the skin that grows out of an
organ known as the hair follicle.
• The length of a hair extends from its root or bulb
embedded in the follicle, continues into a shaft, and
terminates at a tip end.
• It is the shaft, which is composed of three layers—the
cuticle, cortex, and medulla—that is subjected to the
most intense examination by the forensic scientist.
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Cuticle and Cortex
• The cuticle is the scale structure covering the exterior
of the hair.
– The scales always point towards > tip of the hair.
– The scale pattern is useful in species identification.
• The cortex is the main body of the hair shaft.
– Its major forensic importance is the fact that it is embedded
with the pigment granules that impart hair with color.
– The color, shape, and distribution of these granules provide the
criminalist with important points of comparison among the hairs
of different individuals.
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Examination of Hair
Comprehension Assessment:
Look familiar? Label the sections of the skin…
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Medulla
The medulla is a cellular column running through the center of the hair.
• The medullary index measures the diameter of the medulla relative
to the diameter of the hair shaft.
• For humans, the medulla generally occupies less than one-third the
diameter of the shaft, while for animals it is generally one-half or
greater.
• The medulla may be continuous, interrupted, fragmented, or absent.
• The presence of the medulla vary from individual to individual and
even among hairs of a given individual.
• Medullae also have different shapes, depending the species.
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Root
• The hair root is determined by hair’s current
growth phase:
- Anagen phase
- Catogen phase
- Telogen phase
• When pulled from the head, some white or clear
looking tissue surrounding the hair’s shaft near the
root may be found. This is called a follicular tag.
• By using DNA analysis on the follicular tag, the hair
may be individualized.
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Comparing Strands
• The comparison microscope is an indispensable tool for
comparing the morphological characteristics of hair.
• Scale structure, medullary index, and medullary shape are
particularly important in animal hair identification.
• When comparing strands of human hair, the criminalist is
particularly interested in matching the color, length, and
diameter.
• Other important features for comparing human hair are:
–The presence or absence of a medulla.
–The distribution, shape, and color intensity of the
pigment granules present in the cortex.
• The most common request is to determine whether or not hair recovered
at the crime scene compares to hair removed from the suspect.
• However, microscopic hair examinations tend to be subjective and
highly dependent on the skills and integrity of the analyst. For this reason
a reported hair comparison must contain DNA information.
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GET A NUMBER 2 YELLOW PENCIL WITH ERASER
PULL 1 STRAND OF YOUR HAIR OUT (BIG BABY!)
• THE STRUCTURE OF A HAIR CAN BE COMPARED TO A
NUMBER 2 PENCIL
• LAY YOUR PENCIL DOWN NEXT TO THE STRAND OF HAIR
• NOW THINK OF THE PENCIL AS YOUR HAIR AND
ANSWER THE QUESTIONS ON THE WORKSHEET WITH THE
PENCIL.
COMPREHENSION ASSESSMENT: NEXT PAGE
12
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Questions
• Can the body area from which a hair originated be
determined?
• Can the racial origin of hair be determined?
• Can the age and sex of an individual be determined
from a hair sample?
• Is it possible to determine if a hair was forcibly
removed from the body?
• Are efforts being made to individualize human hair?
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ANSWERS TO YOUR ASSESSMENT
1. ORIGINATION CAN ONLY BE ASSUMED/SOMATIC ORIGIN
(UNLESS MITOCHONDRIAL DNA IS FOUND) IT WILL BE
CHALLENGED IN COURT BY LAWYERS.
2. RACIAL ORGIN CAN ONLY BE ASSUMED (UNLESS
MITOCHONDRIAL DNA IS FOUND) IT WILL BE CHALLENGED IN
COURT BY LAWYERS.
3. AGE AND SEX OF HAIR SAMPLES CAN NOT BE DETERMINED ONLY
ASSUMED (UNLESS MITOCHONDRIAL DNA IS FOUND) IT ALL WILL
BE CHALLENGED IN COURT BY LAWYERS.
4. YES, IF HAIR IS FORCIBLY REMOVED FROM THE BODY, THE
DYNAMICS OF THE HAIR STRAND WILL SHOW “TEARING, CUTTING,
PULLED OR RIPPED OUT ROOTS, ETC. AGAIN, IT WILL ALWAYS BE
CHALLENGED IN COURT.
5. YES! FORENSIC SCIENCE IS ALWAYS LOOKING FOR NEW
TECHNOLOGY AND METHODS TO IDENTIFY TRACE EVIDENCE.
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Major Elements of Hair
1. Keratin is a protein that makes up most
of the hair shaft.
2. Melanin is a pigment that gives hair its
color.
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3. Redheads have pheomelanin
instead of melanin.
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Hair
Treatments
Typical Adult Hair
Split Ends(Cuticle Damage)
Human Hair with split ends
Baby Hair
African
Dark,
Blonde White
Asian
Caucasian
1. The cortex is the main body of a hair
(compared to the wooden portion of a
pencil)
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2. The medulla is the central cell of the
cortex (compared to the lead of a
pencil). The medulla is not present in
every hair.
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3. The cuticle is a layer of scales covering
the hair shaft (compared to a layer of
yellow paint on a pencil).
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4. The root is also known as the
“proximal end” (compared to the
eraser on a pencil).
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5. The tip is also known as the “distal
end” (compared to the sharpened tip
of a pencil).
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Characteristic
Comparisons
1. Pigment colors (light,
medium, dark, reddish
brown, brown, black, etc.)
2. Pigment Sizes (fine, moderate, large)
3. Pigment density (light, moderate,
heavy)
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Hair and DNA
• Recent major breakthroughs in DNA profiling have extended this
technology to the individualization of human hair.
• The probability of detecting DNA in hair roots is more likely for
hair being examined in its anagen or early growth phase as
opposed to its catagen (middle) or telogen (final) phases.
• Often, when hair is forcibly removed, a follicular tag—a
white/clear looking piece of tissue surrounding the hair’s shaft
near the root—may be present.
• This has proven to be a rich source of nuclear DNA associated
with hair.
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Hair and Mitochondrial DNA
• Mitochondrial DNA can be extracted from the hair shaft.
• Mitochondrial DNA is found in cellular material located outside of
the nucleus and it is transmitted only from the mother to child.
• Mitochondrial DNA has a high frequency of occurrence in a
population and thus cannot be used to individualize a hair, but it
does provide valuable corroboration of a morphological hair
comparison.
• As a rule, all positive microscopical hair comparisons must be
confirmed by DNA analysis.
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HAIR TYPING
SOMATIC ORIGIN – hairs from different parts of the body have
different characteristics
1. Head hairs are typically straighter than other hair on the body.
They are generally softer, and are the most likely to have color
treatments.
2. Pubic hairs are typically shorter in diameter, with wide variations.
Buckling is a special characteristic found in pubic hairs.
Draw what you believe buckling means on your paper
Be appropriate Gomers!
3. Limb hairs tend to be short and soft. Their tips are usually frayed
or abraded.
4. Facial hairs are very short with irregular or triangular cross
sections. Their medullae may be very broad, even double.
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Collection and Preservation
• As a general rule, forensic hair comparisons involve either head
hair or pubic hair.
• The collection of 20-50 full-length hairs from all areas of the scalp
will normally ensure a representative sampling of head hair. Most
departments do not collect that many hairs.
• A minimum collection 12-24 full-length pubic hairs should cover
the range of characteristics present in pubic hair.
• Hair samples are also collected from the victim of suspicious
deaths during an autopsy.
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Vocabulary Quiz
AH GEEZ
TOLD YOU SO!
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Types of Fibers
• Natural fibers are derived in whole from animal or plant sources.
For example:
– Wool
– Mohair
– Cashmere
– Furs
– Cotton
• Man-made fibers are manufactured.
– Regenerated fibers are manufactured from natural raw
materials and include rayon, acetate, and triacetate.
– Synthetic fibers are produced solely from synthetic chemicals
and include nylons, polyesters, and acrylics.
http://youtu.be/yeAwJwuUQH8
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Fiber Evidence
• The quality of the fiber evidence depends on the ability of the
criminalist to identify the origin of the fiber or at least be able to
narrow the possibilities to a limited number of sources. The
forensic value of fiber evidence is its diversity in our environment.
• Obviously, if the examiner is presented with fabrics that can be
exactly fitted together at their torn edges, it is a virtual certainty
that the fabrics were of common origin.
• Microscopic comparisons between questioned and
standard/reference fibers are initially undertaken for color and
diameter characteristics, using a comparison microscope.
• Other morphological features that could be important in
comparing fibers are:
1. Lengthwise striations on the surface of the fiber.
2. The presence of delustering particles that reduce shine.
3. The cross-sectional shape of the fiber.
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Methods for Fiber Comparison
• The microspectrophotometer is a combination of a
traditional light microscope and a spectrophotometer.
It allows a forensic analyst to view an object under a
microscope while simultaneously obtaining its visible of
infrared absorption pattern.
• The visible light microspectrophotometer is a
convenient way for analysts to compare the colors of
fibers through spectral patterns.
• Infrared spectrophotometry is a rapid and reliable
method for identifying the generic class of fibers.
• The molecules that compose a manufactured fiber
selectively absorb infrared light to form a
characteristic pattern.
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Fiber Collection and Preservation
• FORENSIC investigator’s search/collect strands of
fibers to identify and preserve potential crime scene
fiber evidence.
• Clothing should be packaged carefully in separate
brown paper or brown paper bags. Depends on
team policy.
• If it is necessary to remove a fiber from an object, the
investigator must use clean forceps (tweezers), place
it on a small sheet of paper, or plastic sheet. Carefully
cover the hair with another piece of paper or plastic
and label. Label and Package in an evidence
envelope to size.
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Vocabulary Quiz
Crime scene investigators (yah, yah, yah, students count)
DON’T WHINE!
AFTER YOU ARE DONE WITH YOUR VOCAB.
1. READ & ANALYZE THE HAIR AND FIBER ARTICLE. DON’T HIGHLIGHT
THE ENTIRE THING. WRITE 5 “GOOD” TEXT DEPENDENT QUESTIONS.
2. MAKE SURE YOU ARE ABLE TO IDENTIFY HAIR TYPING AND OTHER
CHARACTERISTICS OF HAIR AND FIBER TO BE SUCCESSFUL ON THE
TEST.
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Forensic Science Hair Lab
Follow the directions in your teams
(Lead Detectives delegate orders and are responsible)
“Trouble goes to the top and runs down from there”
1. Each individual in the team must make 10 fold packages. (we
will be using the extras later in labs)
2. Collect 2 hairs from each of your team members.
3. All Team members place 1 of the 2 hairs in a container. Label
Control “Case # is 2014 1234567 (also referred to as DR #)
4. Take the second hair and place individual hairs in separate fold
packages. Label Evidence.
5. Should have (if) 4 team members, 4 control packages and 4
crime scene packages.
6. Now, swap your 8 with another team. (repeat with every team)
7. Identify which crime scene hair matches which control sample.
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Forensic Science Fiber Lab
Discover fiber typing using the microscopes.
Document the differences amongst fiber types.
Compare the fibers to your unit packet fiber picture
examples.
Note and document the differences between NATURAL
AND SYNTHETIC FIBERS
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