HAIR

Hair As TRACE EVIDENCE

• Human hair is one of the most frequently
recovered types of biological forensic evidence
and the accurate identification of its origin.
• Examination of hair is important for
identification in investigation at scene of
crime.
• Hair on weapon or clothes give important
information regarding the crime such as
accident, rape, etc.
• Poison can be detected in cases of chronic
metal poisoning as well as occupational
poisoning.
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 EXAMINATION OF HAIR
PHYSICAL EXAMINATION
The points to be considered in the examination of
hair are ,
1. The nature, that is if the material is hair or
some other fiber.
2. If it is hair, its source, whether human or
animal.
3. If human, the race, age, sex, situation are
special features for identification.
4. Evidence related to suspected crime.
5. In case of dead bodies time since death.
 COLLECTION OF MATERIAL
Take a transparent glass rod with its pointed
end if you touch suspected area, the hair will
stick on it. Gently transfer it to glass slide and
examine under high magnification.

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 Hair Morphology
• The most basic
components of hair are
keratin, a very strong
protein that is resistant
to decomposition, and
melanin, a pigment.
Hair Morphology
• Hairs are dead, cornified
cells. The portion existing
above the epidermis is
called the shaft; below the
epidermis, the root is
embedded in the hair
follicle.
• The hair shaft is composed
of three layers:
− Outer cuticle
− Cortex
− Central medulla
• The medulla is a central core of cells that runs
Medulla
through the center of the cortex.
– Continuous
– Fragmented
– Interrupted
• In human hairs, the medulla is generally amorphous
in appearance or completely absent.
• In animal hairs, it’s structure is frequently very
regular and well defined.
Medulla

Photomicrograph of a human
hair with no medulla.
Photomicrograph of a hair
with trace medulla.

Photomicrograph of a hair with

a clear, continuous medulla.
 MEDULLARY index

• Medullary ratio is less than ⅓ in humans and

more than ½ in animals.
 Lanugos HAIR
• Most babies lose their lanugos in the eighth or
ninth month of pregnancy, though some can
be born with remnants of the fine coating still
on their body. However, nearly all lanugos will
be shed by three or four months after birth.
 Racial origin of the hair
• The next step tries to classify the racial origin of
the hair as: negroid, mongoloid, and caucasian,
typically using head hair. Mixed individuals
sometimes exhibit properties of all, and make
classification difficult.
HAIR IN DIFFERENT RACES
For Somatic regions hair’s morphology
Head Hair
nsic Analysis
– Head hairs of the
have Hairs
a soft texture,
cut or split tips, and moderate
shaft diameter.
– Pubic hairs have a course, wiry
texture, tapered, rounded, or
abraded tips. Pubic Hair
– Facial hairs have a triangular
cross-section and a course in
texture.
– Eyelash/Eyebrow hairs are saber-
like in appearance, short, and
stubby.
– Limb hairs are soft, and arc-like in
appearance. Tips are rounded
and abraded; scales rounded due
to wear.
Beard Hair
 Source
From the appearance of the cuticle and
medulla and cortex, and from the examination
of hair in cross-section, an idea may be gained
as to the source of hair.
Human hair Animal hair
⚫Texture Fine and thin Coarse and thick
⚫Cuticle Scales are small, Scales are large,
flattened, polyhedral, wavy
serrated and and do not surround
surround the the shaft completely
shaft completely
⚫Medulla Narrow. May be Broad, always
absent present and
fragmented continues 14
⚫ CORTEX Thick. 4-10 times as Thin. Rarely more
broad as medulla than twice the
breadth of
medulla
⚫ MEDULARY Less than 0.3 More than 0.5
INDEX

⚫ PIGMENT More towards the Uniform,

periphery of cortex peripheral or
central

⚫ Precipitin Specific for human Specific for

test with intact animal
root
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 Types of Animal Hairs - Key
Cat Horse Pig Human

A B C D

G
E Deer
F Dog Rabbit
H Rat
I Human
 Natural Fibers
Many different natural fibers that come from plants
and animals are used in the production of fabric.

Cotton fibers are the plant fibers

most commonly used in textile
materials
wool Fiber The animal fiber
most frequently used in the
production of textile materials,
and the most common originate
from sheep.
 Synthetic Fibers
More than half of all fibers used in the production of
textile materials are synthetic or man-made.
Nylon, rayon, and polyester are all examples of
synthetic fibers.

Cross-section of a
Fibers under a
man-made fiber
microscope
 Description of Fibers
1. Cotton fibers. Flattened and twisted.
They have long tubular cells
2. Silk fiber. Are fine, long filament having no
cells in them.
3. Synthetic fiber. Are non cellular fiber of
varying thickness, elasticity, density, solubility
and chemical composition.

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 Acrylic Yarn
Types of Fibers Nylon Rope
Cotton Yarn

A B C

D E F

Polyester Yarn Rayon Rope Wool Yarn

 EVIDENCE ABOUT CRIME
• According to Locard’s principle of exchange,
animal hair may be found on the human body
and vice versa. Similarly in cases of rape and
other sexual offenses, pubic hair of the assailant
may be found on the body of the victim and vice
versa.
• In case of lacerated injury over head the hair
bulb is crushed while in case incised or stab
wound the hair is sharply cut.
• In homicidal cases the hair of the assailant may
be held in tight grip hand of the victim in state of
cadaveric spasm as a result of struggle.
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• In chronic arsenic poisoning, hair serve as good
material for the detection of the poison.
• In burning cases hair get singed. In fire arm
injury cases singeing of the hair around the
wound indicate short distance of the fire.
• Occupation of a person can be guessed from the
hair if trace element can be detected. When the
person exposed to the substance like arsenic, it
may detected in his hair. In aniline industries the
hair of the workers may have a bluish tinge and
in copper industry worker it may greenish tinge.
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 ESTIMATION OF TIME OF DEATH
• Hair ceases to grow after death but due to drying
and shrinkage of skin ,there is apparent growth of
hair on the face.
• (The rate of growth of hair is 0.4mm/day) and
approximate idea of the time sinced death may be
obtain from this, if the time of last shave in known.
• Loosening of the hair occurs in 48-72 hour after
death. In exhumed bodies, in shallow graves scalp
hair change color in 1 to 3 months, in a deep grave
in about 6 to 12 months.
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