1 Chapter 5 Hair

2 Class evidence Circumstantial evidence – lots of people have same hair color Places someone at the scene Only becomes individual evidence if skin or cells attached – then DNA is the individual evidence

3 “Hair” are the facts… Avg human body has ~ 5 million hairs – most fine, down like Hairs are continuously shed and renewed at a rate of 100/day so not surprising that it is at a crime scene Head hair: Blonds have ~ 120,000 Black, brown ~ 100,000 Redheads ~ 80,000

4 Hair Morphology Protein polymers (molecule consisting of many identical repeating units) Hair grows from a follicle (tube-like structure in the dermis) which is linked to the blood supply so whatever substances are taken into the body they are distributed to the hair growing at that time Hair shaft extends out through the epidermis and ends at the tip

5 Hair Morphology: Hair Shaft Cuticle – clear outer covering; tough overlapping scales Cortex – keratin molecules that run parallel to the length of the shaft; contains pigment that makes hair black, brown, yellow, red; no pigment = white, gray; cortical fusi - air spaces in the cortex that have to be seen w/ high power microscope. Medulla – row of cells along center of cortex; human hairs have either fragmented or no medulla except Native Americans and Asians – continuous medulla

6 Hair Shape Depends on cross section of shaft Round – straight hair Oval - curly Crescent-shaped – kinky Can also be twisted or undulated (slightly wavy)

7 Hair Growth Coarser hairs grow slower and fall out less frequently ~ 1cm per month Replaced every 3 to 5 years 3 stages of growth: Anagen – 80-90% of hair follicles at any one time Catagen – intermediate stage; lasts about 3 weeks Telogen – 8-10% of hair follicles; lasts 2-6 months; loss of hair

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10 Anagen hair root telogen hair root Catagen hair root Recently cut hair ?

11 Hair appearance How would the following appear different: Recently cut Hair in brush Hair pulled out from scalp Cut 2-3 weeks ago Colored hair Unconditioned hair Split ends Over heated (blow dryer, curling iron, etc.)

12 So what exactly can be determined from hair evidence? Whether the source is animal or human Racial origin (sometimes) Location on source’s body If hair has been chemically treated (dyed, permed, straightened) Color If hair was forcefully removed

13 Hair as a chemical indicator Chemicals enter cortex of the hair Drugs Metabolites (product of a substances after a chemical reaction – after body metabolizes the chemical) Vitamins Poisons (heavy metals – arsenic, lead, mercury) Oils in hair may contain substances from environment – smoke from crack; (risk of false positive)

14 Hair from a crime scene 1. Determine human or animal – what type of animal

15 2. Determine race