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