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Hairs Trace Evidence.

Published byBrendan Holt Modified over 9 years ago

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Presentation on theme: "Hairs Trace Evidence."— Presentation transcript:

1 Hairs Trace Evidence

2 Hair as Physical Evidence
Class evidence Removal indicates physical contact between victim and perpetrator Strong evidence to place individual at crime scene Compare hairs by color and structure Extract DNA from root for comparison

3 Characteristics of Hair
Appendage of the skin Grows out of the hair follicle Length of hair extends from follicle  shaft  tip Follicle (root) contains DNA

4 Function of Hair Regulate body temperature (insulation)
Decrease friction Protect against sunlight Sense organ

5 Hair Shaft Three layers: Cuticle: surface of hair
Cortex: main body, contains pigment Medulla: hollow core

6 Hair Diagram

7 Cuticle : Outer Layer Transparent, outer layer
Scales point down from younger end towards older ends of hair

8 Cuticle : Scale Patterns
Human Hair Bat Hair Mink Hair Human or Animal Hair

9 Cortex: Color Layer Largest part of hair shaft
Melanin = pigment granules

10 Cortex: Hair Pigmentation

11 Properties of the Medulla
Medullary index (ratio of medulla:shaft) Pattern (continuous, interrupted, fragmented, or absent) Shape (human vs. animal)

12 Human Medulla Patterns

13 Answers from Hair Body area Racial origin
Age and Sex (infant vs. adult, DNA from root for gender) Forcible removal (more sheath cells) Individualize hair (nuclear DNA in root or mitochondrial DNA from shaft)

14 Body Area Head (scalp) Eyebrows and eyelashes Beard and mustache
Underarm Auxiliary or body hair Pubic hair Pubic Hair Beard Hair Limb Hair

15 Mongoloid (Asian) Hair
Racial Origin Negroid (African) Mongoloid (Asian) Hair Caucasian (European)

16 Scissor-cut Broken Burned Razor-cut

17 Dyed Hair Lice Egg Case

18 DNA Evidence Shaft: mitochondrial DNA (mtDNA) Root: nuclear DNA

19 Hair as Forensic Evidence

20 Hair Collection Collected from crime scene by plucking, shaking and scraping surfaces Use tape over small surfaces Vacuum large surfaces Initial analysis performed under compound microscope

21 Testing For Chemicals Neutron activation analysis (NAA) – identify 14 different elements in hair Antimony, argon, bromine, copper, gold, manganese, silver, sodium, zinc Hair grows about 1.3 cm per month – calculate timeline for exposure to toxins or poison

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