Trace Evidence: Hair Encountered at crime scenes Not good for “individualization” of physical evidence 1. No distinctive chemical properties 2. Although structural pattern exists, great amount of variation Hair provides corroborative evidence to place an individual at a crime scene DNA testing has linked a hair to an individual *only if follicular tissue or root attached *only if hair in particular growth phase *analysis of mitochondrial DNA Combo of microscopic, genetic and ample control samples necessary-good? No, b/c can’t distinguish b/w mDNA and hair structure

Morphology of Hair Cuticle –Scale structure covering exterior of hair –Seen with a “scale mount” Cortex –Main part of the hair shaft –Most forensic evidence: pigment granules-size, arrangement, shape and color Medulla –Looks like a central canal if present; pattern continuous, interrupted, fragmented –“medullary index” = diameter of medulla relative to diameter of shaft expressed as a fraction –Has shape which varies from species to species

Hair Growth Root –produces the hair Phases of Growth 1. Anagen – initial growth; follicle actively producing hair; had follicular tag; 2. Catagen – transition stage; hair bulb shrinks in size 3. Telogen – final growth; hair falls out

Human Hair: Microscopic Features CaucasionNegroidMongoloid Shaft of Hair: extends from skin

Human Medulla Patterns interrupted absentcontinuous

Human Scale Pattern: Pattern of the cuticle

Human Feature For Comparison Body location Length of shaft Medullary index Diameter Presence of absence of medulla Distribution of shape and color intensity of pigment granules present in the cortex Artificial treatment –dye Tip and Base of Hair

Human vs. Animal Medullary index = less than 1/3 Medulla has a shingle like appearance Large portion is cortex Medullary index = greater than ½ Medullar has a patterned shape Small portion is cortex