1. Trace Evidence – hair Chapter 5

2. Function of Hair All mammals have hair All mammals have hair Regulates body temperature Regulates body temperature Decrease friction Decrease friction Protect against sunlight Protect against sunlight Sense organ Sense organ

3. Form and structure Hair follicles are formed when a fetus is 5 months Hair follicles are formed when a fetus is 5 months Body has about 5 million hairs Body has about 5 million hairs Blondes – 120,000 on head Blondes – 120,000 on head Brunettes – 100,000 Brunettes – 100,000 Redheads – 80,000 Redheads – 80,000 We lose about 100 hairs a day. We lose about 100 hairs a day.

5. Root is embedded in the follicle where blood is supplied. Root is embedded in the follicle where blood is supplied. Hair shaft grows through the epidermis. (cuticle, cortex, medulla) Hair shaft grows through the epidermis. (cuticle, cortex, medulla)

6. Cuticle – made of overlapping scales Cuticle – made of overlapping scales – Human scales (imbricate) are finer than animal scales – The scales point from the proximal (near head) to the distal end

7. Cortex Cortex – Made of keratin – Contains pigment (melanin)

8. Medulla Medulla – May be dark or translucent depending whether there is air, liquid, or pigment – Can be continuous, interrupted, fragmented, solid, or none

11. 6 types of hair Head Head Eyebrows and eyelashes Eyebrows and eyelashes Beard and mustache Beard and mustache Underarm Underarm Auxiliary or body Auxiliary or body pubic pubic

12. Hair shapes Straight, curly, kinky Straight, curly, kinky Depends on the shape of the hair cross- section Depends on the shape of the hair cross- section – Round: straight (Asians, Native Am.) – Oval: curly (Americans, Europeans, Mexicans, Middle Eastern descent) – Crescent moon: kinky (African American), dense pigmentation – Beard: coarse and triangular

13. caucasian negroid mongoloid

14. Growth info Grows 1 cm per month Grows 1 cm per month New hair every 3-5 years New hair every 3-5 years 3 stages: 3 stages: – Anagen: up to 5 years – Catagen: intermediate – Telogen: mature (follicle is ready to push out hair – 8-10% of follicles)

15. Mature hairs will have a bulb-like root Mature hairs will have a bulb-like root Immature hair forcibly removed will have follicular sheath present Immature hair forcibly removed will have follicular sheath present Animal roots are typically spear-shaped Animal roots are typically spear-shaped Tip of hair will taper if uncut and not abused Tip of hair will taper if uncut and not abused Tip is squared off, if recently cut (only 2- 3 weeks) Tip is squared off, if recently cut (only 2- 3 weeks)

17. Racial differences European – straight, wavy, pigment granules evenly distributed, oval cross-section, color may be blond, brown, red, or black European – straight, wavy, pigment granules evenly distributed, oval cross-section, color may be blond, brown, red, or black Asian – straight, dense pigment granules, round cross-section, coarse and straight, thick cuticle, continuous medulla Asian – straight, dense pigment granules, round cross-section, coarse and straight, thick cuticle, continuous medulla African – kinky, curly or coiled, dense and clumped pigment granules, flattened cross- section African – kinky, curly or coiled, dense and clumped pigment granules, flattened cross- section

18. Animal vs. Human Animal Pattern of pigmentation varies widely Pattern of pigmentation varies widely Pigment dense toward medulla Pigment dense toward medulla Color found in ovoid bodies and colors change in banded pattern Color found in ovoid bodies and colors change in banded pattern Medullary Index – 0.50 or more Medullary Index – 0.50 or more Human Pigment dense toward cuticle Pigment dense toward cuticle One color along length of hair One color along length of hair Medullary index 0.33 or less Medullary index 0.33 or less

19. Animal Coronal cuticle – looks like a stack of crowns (rodents and bats) Coronal cuticle – looks like a stack of crowns (rodents and bats) Spinous – look like petals (cats, seals, mink) Spinous – look like petals (cats, seals, mink) Human Imbricate – flattened and narrow Imbricate – flattened and narrow

20. Microscopy Phase contrast microscopy – can help see very fine details Phase contrast microscopy – can help see very fine details Fluorescence – will show whether a dye is present Fluorescence – will show whether a dye is present Electron microscopy – magnifies 50,000 times or more Electron microscopy – magnifies 50,000 times or more

21. Testing for substances Dissolving in an organic solvent which breaks down the keratin and releases the chemicals inside the hair Dissolving in an organic solvent which breaks down the keratin and releases the chemicals inside the hair Time since exposure can be measured by using the amount hair grows in one month(1.3cm) Ex: if toxin is found 9cm down from root, when did the person take in the toxin? Time since exposure can be measured by using the amount hair grows in one month(1.3cm) Ex: if toxin is found 9cm down from root, when did the person take in the toxin? Neutron activation analysis – can identify up to 14 different elements in 2cm of hair. The chance for two people to have 9 elements alike is one in a million. Neutron activation analysis – can identify up to 14 different elements in 2cm of hair. The chance for two people to have 9 elements alike is one in a million.

22. What can hair tell us? Animal or human Animal or human Race Race Body location Body location Chemical treatment Chemical treatment Color Color How hair was removed How hair was removed

23. Drugs Drugs Metal poisoning Metal poisoning Things from the environment stick to oils Things from the environment stick to oils Can cause false positives Can cause false positives DNA DNA