FORENSIC TRICHOLOGY
SFS1. Students will recognize and classify various types
of evidence in relation to the definition and scope of
Forensic Science
b. Distinguish and categorize physical and trace evidence
(e.g. … hair)
SFS2. Students will use various scientific techniques to
analyze physical and trace evidence.
b. Analyze the morphology and types of hair.
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ESSENTIAL QUESTIONS
How can you distinguish the types and
layers of hair?
 How can you distinguish animal and
human hair?
 How can you distinguish the growth
periods of hair?
 How can you distinguish one human hair
from another?

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HISTORY
1590 – First operating compound microscope
1847 – Earliest examination of hairs in criminal investigation
1861 – First forensic investigation of human hair
comparison of hair found on victim to those of defendant
1906 – Documented use of hair in forensic investigations to
determine identity
1910 – Microscopic studies of both human and animal hair
1951 – Use of adhesive tape to collect trace evidence
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TYPES OF HAIRS

Primordial hairs – develop from 9 to 22 wks.

Lanugo hairs – fetal body hair shed by 36-40 wks.

Vellus hairs – “peach fuzz” pre-pubescent hair

Terminal hairs – adult hair stimulated to grow by
androgens (male hormones)
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HAIR STRUCTURE
Hair is primarily composed of the
protein keratin and the pigment
melanin
 Hair is both living and dead – the
living part (root) is enclosed
within the follicle, while the dead
part is the shaft

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HAIR STRUCTURE
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Cross-Section of a Hair
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HAIR STRUCTURE
Cuticle - a translucent outer layer of
the hair shaft consisting of scales that
cover the shaft.
Cuticular
scales always point from the
proximal (root) end of the hair to the distal
(tip) end of the hair.
 Not useful in individualizing human hair,
but can be used for species identification
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HAIR STRUCTURE
Cuticle Structure
1. Coronal “crown-like”
Rare in humans
Typical of rodents.
Found in hairs of very
fine diameter.
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HAIR STRUCTURE
Cuticle Structure
2. Spinous “petal-like.”
Never found in humans.
Common in cats, seals,
and minks.
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HAIR STRUCTURE
Cuticle Structure
3. Imbricate “flattened”
Common in humans
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HAIR STRUCTURE
Cortex - is the main body of the hair
Embedded with pigment granules that
give hair its color
 The color, shape and distribution of the
granules provide points for forensic
comparison
 Dyed hair has uniform pigmentation in
cortex and cuticle

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HAIR STRUCTURE
 In
humans, pigment granules are
commonly distributed toward the
cuticle, except in red-haired
individuals.
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HAIR STRUCTURE
 Animal
hairs have the pigment
granules commonly distributed toward
the medulla.
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HAIR STRUCTURE
Medulla - a cellular column running
through the center of the cortex
Presence of medulla varies quite a bit:
even hair to hair
 Useful in distinguishing among animal
species


MEDULLARY INDEX = diameter of the medulla
diameter of the hair shaft
Humans: medullary index < 1/3
Animals: medullary index > 1/2
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Medulla Structure (Animal)
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HAIR STRUCTURE

Medullary Patterns
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Medulla Structure (Human)
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GROWTH AND REPLACEMENT OF
HAIR
Mammalian hair follicles go through three
distinct growth cycles.
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GROWTH AND REPLACEMENT OF
HAIR
Anagen: the active growth phase
Scalp hairs spend 2-7 yrs in this phase and
grow approximately 1 cm/mo.
 Up to 90% of the hairs are in this growth
cycle
 Follicle is attached to the root by the
papilla. The hair must be pulled to be lost.

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GROWTH AND REPLACEMENT OF
HAIR
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GROWTH AND REPLACEMENT OF
HAIR
Catagen: the transitional stage
Lasts two to four weeks
 Only 2% of the hairs are in this phase
 Follicle is losing blood supply and hair is
retreating to the surface

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GROWTH AND REPLACEMENT OF
HAIR
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GROWTH AND REPLACEMENT OF
HAIR
Telogen: the resting phase
 Lasts
two to four months, until hairs fall
out naturally or are forcibly removed
 About 10% to 18% of the hairs are in
this phase
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GROWTH AND REPLACEMENT OF
HAIR
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IDENTIFICATION OF HUMAN HAIR
 The
first step of forensic
identification and comparison of
hairs begins with whole mount
light microscopy.
 The hair(s) in question must be
identified as to species, race and
body (somatic) origin.
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IDENTIFICATION OF HUMAN HAIR
 Human
hairs can be readily
distinguished from animal hairs in
primarily by examining the
cuticles and medullae.
 Individualizing human hairs is
done by examining cortex
features and by analyzing DNA.
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RACIAL ORIGIN

European
Shaft: straight to wavy
 Shaft diameter: moderate with
minimal variation
 Cortex: sparse to moderately
dense with melanin; fairly even
distribution
 Medulla: variable
 Cross-sectional shape: oval

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EXAMPLES OF RACIAL HAIR
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RACIAL ORIGIN

African
Shaft: prominent twist and curl
 Shaft diameter: moderate to fine
with considerable variation
 Cortex: melanin is densely
distributed and arranged in
prominent clumps
 Medulla: fragmented or absent
 Cross-sectional shape: flattened

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EXAMPLES OF RACIAL HAIR
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RACIAL ORIGIN

Asian
Shaft: straight with thick cuticle
 Shaft diameter: coarse with little
or no variation
 Cortex: densely distributed
melanin and often arranged in
large patchy areas or streaks
 Medulla: prominent (often broad
and continuous)
 Cross-sectional shape: round

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EXAMPLES OF RACIAL HAIR
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SOMATIC ORIGIN

Somatic Origin:

Head
 Long with moderate shaft diameter and
diameter variation
 Medulla absent to continuous and relatively
narrow when compared to the structure of
hairs from other body areas
 Often with cut or split tips
 Can show artificial treatment, solar
bleaching, or mechanical damage
 Soft texture, pliable
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SOMATIC ORIGIN

Somatic Origin:

Pubic
Shaft diameter coarse with wide
variations and buckling
 Medulla relatively broad and
usually continuous when present
 Root frequently with tag
 Tip usually tapered, rounded, or
abraded
 Stiff texture, wiry

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SOMATIC ORIGIN

Somatic Origin:

Limb hairs (arm or leg)
 Diameter fine with little variation
 Gross appearance of hair is arc-like in
shape
 Medulla is discontinuous to trace with a
granular appearance
 Tips usually tapered often blunt and
abraded, rounded scale ends due to
wear
 Soft texture
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SOMATIC ORIGIN

Somatic Origin

Beard or Mustache hairs
Diameter very coarse with
irregular or triangular crosssectional shape
 Medulla very broad and
continuous, may be doubled

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IDENTIFICATION OF HUMAN HAIR

Somatic Origin

Chest hairs
Shaft diameter moderate and variable
 Tip often darker in color, long and fine, arclike
 Medulla may be granular
 Stiff texture

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IDENTIFICATION OF HUMAN HAIR

Somatic Origin

Underarm hairs
Resemble pubic hairs in general
appearance, but less wiry
 Medullar appearance similar to limb hairs
 Diameter moderate and variable with less
buckling than pubic hairs
 Tips long and fine, frequently with bleached
appearance

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IDENTIFICATION OF HUMAN HAIR

Somatic Origin:

Other
Eyebrow: Stubby, some diameter fluctuation,
saber-like in appearance
 Eyelash: Short, stubby with little shaft
diameter fluctuation, saber-like in
appearance
 Trunk: A combination of features of limb and
pubic hairs, a transitional hair

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IDENTIFICATION OF HUMAN HAIR
 As
a rule, most forensic
comparisons are conducted
using scalp or pubic hairs.
Body and limb hairs are
generally considered
unsuitable for comparison
purposes.
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VARIATIONS IN COLOR
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COLLECTION AND
EXAMINATION OF HAIR
Always photograph the item and
note its location first before
collecting it.
 Always be sensitive to crosscontamination issues.
 Always wear gloves to collect
evidence.
 Always use clean, unused paper
bindles or containers.

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COLLECTION AND
EXAMINATION OF HAIR
Use fingers or tweezers to collect crime
scene evidence.
 Collect good representative exemplary
(known) hairs from the scalp and/or
pubic region.
 Collect exemplars from both the victim
and suspect.
 Always maintain the chain of custody.

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COMPARATIVE MICROSCOPY
Skillful microscopic technique
provides the forensic hair examiner
with a highly discriminating means to
examine and compare hair, and
utilizes various types of microscopes.
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COMPARATIVE MICROSCOPY

Stereomicroscope - permits gross
observations of the hairs; allows a rapid
overview of the range of characteristics.
 Polarizing microscope - delineates the
hair’s finer structural characteristics.
 Transmitted light microscope - allows a
side-by-side comparison of the known and
questioned hairs. Hairs are compared from
their root end to their tip end.
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CONCLUSION AND REPORT
WRITING

Forensic laboratory reports of hair
comparisons normally will provide one of
three answers:



The hairs matched in microscopic
characteristics, indicating an association.
The hairs are not alike and therefore did not
come from the same person.
No conclusion can be drawn from the evidence.
This may be due to insufficient specimen, racial
mixtures, or unsuitable exemplars.
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DNA Analysis

Nuclear DNA
Combination of both parents
 Hair root/follicle


Mitochondrial DNA
Mother’s lineage only
 Hair shaft

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