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Published byBryan Morgan Modified over 9 years ago
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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
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Resistant to decomposition and maintains its structure.
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The average human body has about 5 million hairs!
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The average number of Brown/Black scalp hairs: 100,000!
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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!
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50 - 100
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Between 15 and 30 years of age
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0.35 mm/day or about 1 cm/month
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In summer
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NOVEMBER
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Structure from which hair grows Lies below epidermis Can differentiate Between species Sticks out of skin
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The organ that hair grows out of
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1. The CUTICLE is the outside covering
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The cuticle protects the cortex
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Scale patterns are not useful forensically because the scale patterns in humans are the same
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In animals, a variety of scale patterns are found bat mink deer
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Scales always point toward the tip of hair (1) mosaic
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The bulk of each hair’s mass is contained in the cortex.
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contains the various proteins and bonds which determine the curliness or straightness of the hair.
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Pigment granules that give hair its color
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Air spaces Usually found near the root But can be found Throughout the Hair shaft
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-Formed by cells running through hair -Amorphous in appearance
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= diameter of medulla diameter of hair The medulla is approximately.005 mm In width This hair is. 030 mm in diameter The Medullary Index =.005 mm.030 mm = 1/6
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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
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continuous fragmented absent Interrupted or intermittent
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(1) Uni serial (2) multi serial
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Mountain lion
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Hair as Evidence Determine… 1. Human or animal? In Humans: Medullary Index < 1/3 In Other Animals: Medullary Index ≥ 1/2
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Negroid hairs Negroid or African origin hairs are usually curly with a flattened cross section and appear to be curly, wavy, or coiled.
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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.
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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.
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a. Scalp hairs - all about the same diameter b. Beard hairs - coarse, blunt tips c. Pubic hairs - short, curly
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Forcibly removed hair will include the root tip
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contains tissue surrounding hair shaft Contains DNA!!
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a. roots
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Removes color, yellow tint
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Hair testing is considered accurate and can go back as far as 90 days
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1. Color, straight vs wavy vs curly, etc.
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of medulla
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In the cortex
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Vitamin deficiency fungus nits (lice) Or diseases
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Function of the root – nourishment for hair growth
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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
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The root bulb shrinks The growth rate decreases Lasts 2-3 weeks
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RESTING phase 2-6 months
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Is also called the SHEDDING phase
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50 – 100 hairs per day
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For 2 – 5 years
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85% - 90%
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