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Hair
Hair
…and more hair.
Hair as EvidenceCan only compare head hair to head hairor pubic hair to another pubic hair
Control hairs from suspect: 50 full length head hairs minimum of 24 pubic hairs
HAIR is useful as forensic evidence because its protein polymers are…
Resistant to decomposition and maintains its structure.
The average human body has about 5 million hairs!
Some HAIRY facts…
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!
Blondes have 120,000
Redheads have at least80,000
Average daily # of hairs shed:
50 - 100
Fastest Growth..Between 15 and 30
years of age
Slow Growth..
Average Scalp hair growth… 0.35 mm/day or about 1
cm/month
Hair grows faster … In summer
Month of greatest hair shed in Northern Temperate zone:
NOVEMBER
Hair Morphology (structure)
Structure from which hair grows
Lies below epidermisCan differentiateBetween species
Sticks out of skin
The organ that hair grows out of
Cross Section of hairThe Hair shaft is made up of….
1. The CUTICLE is the outside covering
a. SCALES cover the cuticle
The cuticle protects the cortex
In Humans
Scale patterns are not useful forensically
because the scale patterns in humans are the same
In animals, a variety of scale patterns are found
bat mink
deer
Scales always point toward the tip of hair
(1) mosaic
(2) pectinate
(3) imbricate
(4) petal
(5) Diamond petal
(6) chevron
2. Cortex – gives hair its shape
The bulk of each hair’s mass is contained in the cortex.
The CORTEX… contains the various proteins and bonds
which determine the curliness or straightness of the hair.
a. melanin Pigment granules that give hair its
color
b. Cortical fusiAir spaces
Usually found near the root
But can be foundThroughout the Hair shaft
3. Medulla – “central canal”-Formed by cells running through hair-Amorphous in appearance
Medullary Index = diameter of medulla diameter of hair
The medulla isapproximately
.005 mmIn width
This hair is .030 mm in
diameter
The Medullary Index = .005 mm .030 mm = 1/6
Degree of variations in medullas
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
a. Types of medullas (Human)
continuousfragmented absent
Interrupted or
intermittent
b. Patterns (other animals)(1) Uniserial
(2) multiserial
(3) Vacuolated Mountain lion
(4) lattice
(5) Amorphous – without a clear form
Hair as EvidenceDetermine…
1. Human or animal? In Humans: Medullary Index < 1/3 In Other Animals: Medullary Index ≥ 1/2
2. Race (ethnicity)
Negroid hairs
Negroid or African origin hairs are usually curly with a flattened cross section and appear to be curly, wavy, or coiled.
Caucasian hairs
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 hairs
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.
3. Origin –from which part of body
a. Scalp hairs - all about the same diameter
b. Beard hairs - coarse, blunt tips
c. Pubic hairs - short, curly
4. Manner in which hair was removed
Forcibly removed hair will include the root tip
Follicular Tag contains tissue surrounding hair shaft
Contains DNA!!
5. Treated Hair a. roots
b. Dye present in cuticle or cortex
c. Bleached hair
Removes color, yellow tint
6. Drug Testing
Hair testing is considered accurate and can go back as far as 90 days
Hair Comparison
1. Color, straight vs wavy vs curly, etc.
2. Presence or absence.. of medulla
3. Pigment Granules
In the cortex
4. Dyed or bleached?
5. Abnormalities Vitamin deficiency fungus
nits (lice)
Or diseases
Hair GrowthFunction 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
Anagen hair roots
2. Catagen The root bulb shrinks The growth rate decreases Lasts 2-3 weeks
Catagen –TRANSITION stage
3. Telogen
RESTING phase 2-6 months
Telogen plase Is also called the SHEDDING phase
Hair shed rate
50 – 100 hairs per day
Each Hair is in Growth phase (Anagen)
For 2 – 5 years
% Hair in Growth Phase (Anagen)
85% - 90%
