0. Hairs
Trace Evidence

1. Hair as Physical Evidence
Class evidence
Removal indicates physical contact between victim and perpetrator- Locard’s Principle

2. Hair as Physical Evidence
Not good evidence by itself.
Present with other evidence it becomes stronger

3. Hair as Physical Evidence
Compare hairs by color and structure
Extract DNA from (if present) root for comparison – Individual evidence. **Now hair is excellent evidence

4. 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

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, or absent)
Shape (human vs. animal)

12. Human Medulla Patterns
Interrupted Absent Continuous

13. Answers from Hair Body area Racial origin
Age and Sex (infant vs. adult, DNA from root for gender)
Forcible removal (more sheath cells)

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. Racial Origin
African American
Asian
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. Growth Stages of the Hair:
Anagen Stage:  The active growth phase of the hair follicle. 
Catagen Stage:  The transition period between growth and rest.  Hair continues to grow, but at a decreasing rate.  The root bulb looks elongated from being pushed out of the follicle.
Telogen:  The rest period for the follicle.  The current hair is shed and no new growth takes place for a period of time.

21. Hair as Forensic Evidence

22. 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
Collect 50 hairs from suspect for comparison. Not all hairs are the same

23. 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