Forensic Value of Hair
Hair is class evidence – morphorlogy
(how it looks), index (how thick the
medula is), color
Mitochondrial DNA from shaft. All
mitochondria comes from egg only, not
sperm. So ONLY maternal lineage
If hair bulb (root) is present, then can get
nuclear (individual DNA) from it
Hair is Class evidence ONLY
A piece of hair cannot be individualized to a particular head/person Rather it can be characterized and classified
Comparative Microscope Allows technician to compare two hairs side by
side Comparison Microscope Two matching hairs
When is hair evidence
important in a case?
Animal or Human determination
Body area determination
Race association with hair
Animal vs Human Hair
The medulla is a string of dots in animal hair.
humans frequently lack medulla
Pigment in animal hair tend to clump, human
hair pigments more evenly distributed
Animal hair has distinct banding
Human hair color is constant throughout
MOST IMPORTANT – animal medulla is
pretty thick, while in humans the medulla is
thin or lacking
The Medulla Index is the ratio of the medulla width to
the entire hair width. It is much bigger in animals
than in humans
Human hair
Dog hair
Animals have a more patterned
medulla than humans
HUMAN HAIR
• The root is club-shaped
• Consistent in color and
pigmentation throughout
the length of the hair
• Medullary index is less
than 1/3
• Pigment is evenly
distributed, slightly more
dense near the cuticle
Pigment Distribution in Human
Hair • Pigment granules are small,
dark, and solid structures
• They vary in color, size, and
distribution in a single hair.
• In humans, pigment granules
are commonly distributed
toward the outer edge of cortex
• The exception is red-haired
individuals, granules are
concentrated along the center of
the hair
Brown Human Hair
Red Human Hair
Ovoid bodies found in Dog
Hair
Ovoid bodies are abundant
in Cattle hair
The cuticle scales are very
distinct from species to species
A species is defined as organisms that can
interbreed and produce fertile offspring
Rabbit – Spinous cuticle
pattern
Can you identify the animal hairs shown?
Think About It …
(1) In which samples are we viewing the cuticle? How do they compare?
(2) In which samples are we viewing the medulla? How do they compare?
(3) What characteristics can be used to identify hair samples?
Types of Animal Hairs - Key
A B C D
E F
G
I H
Cat Horse Pig Human
Deer Dog Rat Rabbit Human
Hairs might show signs of
cutting
Which hair was cut by a razor?
Which was cut with scissors?
Which split on its own?
Pubic Hairs
One of the kinds of evidence where the mere
presence will suggest foul play.
Pubic Hairs
Coarse, Wiry
Diameter’s show a lot of
variation
Buckling and tapered ends
are common
Racial Type of Hair
Compare these cross-sections of three hairs, all of different racial types:
(left) Asian, (center) Caucasoid, (right) African
African-Origin Hair
• Shaft diameter: moderate
to fine with considerable
variation
• Pigment granules: densely
distributed (hair shaft may
be opaque) and arranged
in prominent clumps
• Shaft: prominent twist and
curl
Asian-Origin Hair
• Shaft diameter: coarse and
usually with little or no
variation
• Pigment granules: densely
distributed and often
arranged in large patchy
areas or streaks
• Medulla: prominent (often
broad and continuous)
• Cuticle: thick
Caucasian-Origin Hair
• Shaft diameter: moderate with
minimal variation (mean
diameter for human head hairs -
80um)
• Pigment granules: sparse to
moderately dense with fairly
even distribution
Epidermis - protects skin, renewed
frequently
Sebaceous gland, sebum, lubricates and
waterproofs skin and hair, mostly on face
and scalp, not palms or soles
All the blood supply to the hair comes
from the bottom portion of the hair in the
dermis.
