Forensic Hair Analysis

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Human Hair Analysis
Hair and Fiber 1
Hair Analysis
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Encountered in a wide variety of crimes
Especially useful in rape cases
 Also useful in illegal drug usage cases
(toxicology)
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Many attempts have been made to
positively identify a suspect but all have
failed
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Hair is usually class characteristic only
Typically need more than one
Vital Properties
Species identification
 Color/Pigment
 Length
 Diameter
 Internal characteristics
 Dye/Bleaching
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Hair as Evidence
Hair evidence is evaluated by physical
microscopy or chemical analysis
 Toxicology

Hair acts like a time capsule
 Base of hair shows most recent use
 Protein structure “freezes” evidence of
drugs, heavy metals, etc. in hair
 Typical human head hair growth is 1 cm per
month
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Rape/Homicide
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Source of DNA in follicular tissue
Hair as Evidence
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Species identification
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Most species of mammals are distinctly
different from each other under a
microscope
Human ethnicity
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Can usually identify ethnicity in humans
Human Ethnicity
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Caucasoid
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Mongoloid
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Usually straight or wavy
Evenly distributed, usually fine pigmentation
Oval to round cross section
Fragmented/absent medulla
Usually straight
Usually even, dense pigmentation
Typical human hair cross
Continuous medulla (defining characteristic)
sections
Negroid
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Kinky
Dense, unevenly distributed pigment
Flat to oval cross section
Fragmented/absent medulla
“Buckling” often seen
Hair Evidence Myths
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Age
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Age can not be determined with any amount of
certainty
Only infants seem to have distinct characteristics
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Usually very fine
Gender
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Gender can not be determined without follicle and
DNA analysis
Male/Female structure identical
Differences mainly genetic in nature
Hair Evidence Myths

DNA extraction
Can be extracted from follicular tissue or
root (in some cases)
 Cut hair without the root usually does not
contain enough DNA to type
 If forcefully removed, follicle tissue w/ DNA
likely attached to root
 Hair that falls out naturally does not contain
adhering tissue
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Body Hair Types
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Forensically valuable hair
 Scalp hair
 Little diameter differences
 Uniform pigment
 Exposure to environmental conditions
make immediate processing vital
 Pubic hair
 Vary widely in diameter
 Usually curly
 Short length
 Less exposure to elements allows for
collection long after crime
Body Hair Types

Lesser forensic value
 Most other body hairs are too variable in
appearance to be valuable for forensics
 Characteristics are in no way linked to patterns
found on scalp hair
 Can be used to determine a suspect’s presence at
scene but not often used
 Three types
 Limb - arm, leg
 Fringe hair - neck, sideburns, upper leg, back
 Axillary - eyebrows, nose, underarm
Hair Structure
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Structural components
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Epidermis
 Outermost layer of skin
 Pitted with hair follicles
Root
 Portion of hair below skin
Follicle
 Only segment of hair that is
living
 Source cells from which hair
grows
 Below skin in the bulb
Hair Structure
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Structural components
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Arrector (Erector) Muscle
 Can cause hair to stand on
end
 Also source of
“goosebumps”
 Many animals have control
over these muscles
Hair Structure

Structural components
 Hair shaft
 Composed of protein
keratin
 Structurally the same as
fingernails
 Three layers
 Cuticle, Cortex,
Medulla
Hair Structure

Structural components
 Cuticle
 Provides support for hair
 Non-living
 Consists of overlapping
external scales different
than most other mammals
 Scales very resistant to
decomposition
 Makes for perfect
physical evidence
Hair Structure
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Structural components
 Cortex
 Inner layer of hair
 Contain pigment granules
 Melanin protein
 Distribution of pigment
helps to determine
particular individuals
Hair Structure
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Structural components
 Medulla
 A “tube” of cells that run up
the center of the cortex
 Width of medulla is vitally
important in identifying
species
 Ratio of hair width to medulla
width is called medullary index
Hair Structure

Structural components
 Medulla
 Humans have less than 1/3
medulla, most other animals
at least ½
Comparison of
human hair
(left), deer hair
(top) and dog
hair (right)
Hair Structure

Structural components
 Medulla
 Not always present in
certain ethnicities
 One person can have
multiple medulla structures
 Continuous
 Interrupted
 Fragmented
Human Medulla Types
Typical human medulla types. From left to right:
Continuous, Interrupted, Fragmented.
Hair Structure
Artist’s conception and electron microscope images of a human hair with
cuticle, cortex and (to a lesser extent) medulla
Hair Growth

Growth cycle has three distinct phases
Hair can stay on head for approx. 6 years
 If forcefully pulled out and in one of first
two phases, follicle tissue will likely be
found with the hair follicle
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(right) Diagram
showing the
three phases of
hair growth
Hair Growth
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Anagen
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Up to six years
Root attached to follicle
Root will have a “flame”
shape
If pulled out, will usu.
have follicular tissue and
show evidence of
stretching/force
Growth originates at base
of hair and grows up
80-90% of all hair will be
in this phase
(Above)Electron microscope image
showing new anagen follicles erupting
from the epidermis. (Below) A typical
anagen follicle with attached tissue.
Hair Growth
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Catagen
Two to three weeks
 Growth slower
 Root shrinks and is pushed out of follicle
 Usu. has a shrunken appearance
 2% of all hair
 Transition phase
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Hair Growth
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Telogen
Two to six months
 No growth
 Root has a club shape
with no tissue
 Is shed naturally
 10-18% of all hair
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A typical telogen hair
follicle. Note the absence of
follicular tissue.
Hair Microscopy
Damaged cuticle showing
loose scales.
Typical wear and tear
with dislodged scales and
other debris on hair
follicle.
Hair Microscopy
Severely damaged hair
that may be the result of
braiding or forceful
removal.
A “split end” on a hair follicle.
Also note evidence of cutting
by sharp scissors. Electric
clippers usually leave much
more ragged marks.
Hair Microscopy
A twisted/stretched root…clear
indicator of forceful removal.
Tight, twisted
appearance and scorch
marks of hair exposed
to high heat.
The Atlanta Child Murders
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1979-1981, 29 black males were murdered (ages 7-16
except for last 7 who were 17-27)
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Only common evidence were fibers and presence of
dog hair
Two artificial fibers ID’ed
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After info. leaked to press, M.O. changed and bodies were
dumped in river
PD staked out Chatahoochee River
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Strangled, beaten, asphyxiated
PD heard a loud splash and stopped a suspect (Wayne
Williams)
Claimed it was garbage
Suspect released but body later found nearby w/
single carpet fiber in hair
The Atlanta Child Murders
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Warrant obtained for Williams’ house and
found matching carpet and dog hair/fibers
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Expert assistance obtained from DuPont corporation
Exhaustive use of statistical likelihood of
particular carpet being found in a single
Atlanta home 1:7792
Additional fiber matches w/ victims’ found
from Williams’ car
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Chevrolet assisted in this part of investigation
Statistical possibility 1:3828
The Atlanta Child Murders
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Combined, 1:30 million
chance of both matches
being achieved
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In total, 29 fiber type
matches found between
Williams’ possessions and
victims
Found guilty after 12 hours
of deliberation
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Serving 2 life sentences
Still maintains innocence
and has attempted retrials
Wayne Williams at his
arraignment in February 1982.
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