Hair

…and more hair.

Hair as Evidence

Can 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 fusi

Air 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%