Can only compare head hair to head hair
or pubic hair to another pubic hair
Control hairs from suspect:
50 full length head hairs
minimum of 24 pubic hairs
Resistant to
decomposition
and maintains
its structure.

The average human body has about 5
million hairs!
The average number
of Brown/Black
scalp hairs:
100,000!
On the average, the human scalp has
100,000 hair follicles. You are born with as
many hair follicles as you are ever going to
have!
50 - 100
Between 15 and 30
years of age
0.35 mm/day or about 1 cm/month
In summer
NOVEMBER
Sticks out of skin
Structure from
which hair grows
Lies below epidermis
Can differentiate
Between species
The organ that
hair grows out of
1. The CUTICLE is
the outside covering
The cuticle
protects
the cortex
Scale patterns are not useful forensically
because the scale patterns
in humans are the same
In animals,
a variety of scale patterns
are found
deer
bat
mink
Scales always point toward the tip of hair
(1) mosaic
The bulk of each hair’s mass is
contained in the cortex.
contains the various proteins and bonds which
determine the curliness or straightness of the
hair.

Pigment granules that give hair its color
Air spaces
Usually found
near the root
But can be found
Throughout the
Hair shaft
-Formed by cells
running through hair
-Amorphous in
appearance
= diameter of medulla
diameter of hair
The medulla is
approximately
.005 mm
In width
The Medullary Index = .005 mm
.030 mm
= 1/6
This hair is
.030 mm in
diameter
Vary from one individual to another
 And even between hairs of one person

Human hair
Medulla index < 1/3
in other animals: ½ or greater
Interrupted
or
intermittent
fragmented
absent
continuous
(1)
Uniserial
(2)
multiserial
Mountain lion
Hair as Evidence
Determine…
1. Human or animal?
In Humans:
Medullary Index < 1/3
In Other Animals:
Medullary Index ≥ 1/2
Negroid hairs
Negroid or African origin hairs are
usually curly with a flattened cross
section and appear to be curly,
wavy, or coiled.
Caucasoid or Caucasian origin hairs are
normally fine to medium coarseness,
oval cross-section, straight or wavy in
appearance, and colors range from
blonde to brown to black.
Mongoloid or Asian origin hairs are
normally coarse, straight, with a wider
diameter than hairs of the Caucasoid
and Negroid hairs. The outer layer of the
hair is usually much thicker than that of
the other racial groups.
b.
Scalp hairs - all about the same diameter
Beard hairs - coarse, blunt tips
c.
Pubic hairs - short, curly
a.
Forcibly removed hair will include the root
tip
contains tissue surrounding hair shaft
Contains DNA!!
a. roots
Removes color, yellow tint
Hair testing is
considered accurate
and can go back as
far as 90 days
1. Color,
straight vs
wavy vs
curly, etc.
of medulla
In the cortex
Vitamin deficiency
fungus
nits (lice)
Or diseases
Function of the root
– nourishment for
hair growth
A. TERMINOLOGY
Phases of growth
1. anagen -
the root
is attached
to the follicle
GROWTH PHASE
lasts 2-6 yrs
90%of hair is in anagen
The root bulb shrinks
 The growth rate decreases
 Lasts 2-3 weeks

RESTING phase

2-6 months
Is also called the
SHEDDING phase
50 – 100 hairs per day
For 2 – 5 years
85% - 90%