hair analysis

characteristics of hair

adhere to surfaces; doesnt decompose; class evidence

Functions of hair

Regulates body temperature; decreases friction; protect skin against sunlight; acts as a sense organ

anagen stage

Active growth (80-90% of all hair)

Catagen stage

Hair stops growing

telogen stage

Dormant and resting; hair is shed at the end of the stage

follicule

Cub-shaped structure that contains a network of blood vessels that supply nutrients

Contains cells with DNA

Oil gland

hair shaft

Non Growing part of hair

Contains mitochondrial DNA

Composed of a protein called Keratin

inner medula

Center of the hair

cortex

The largest part of the hair shaft that contains the melanin granules (gives the hair the color)

Outer cuticle

Protects the inner layers; made up of overlapping scales

DNA source

Hairs with an attached follicle or root

Contain nuclear DNA

Provide individual evidence

without root or follicule

Contain mitochondrial DNA

Reveal family relationships

6 types of hair on body

Head, eyebrows and eyelashes, beard and mustaches, under arm, body hair, pubic

treated hair

bleaching, dyeing, Determining PMI (post-mortem interval) - can possibly tell when someone died based on treated hair

Hair grows at the rate of 1.3 cm/month or .44mm a day but can be affected by many other factors like age, stress, and hormones

key physical characteristics, but only generalities

European (straight or wavy, C/S oval or round)

Asian (straight, C/S round with large diameter)

African (kinky or curly, C/S flattened with small diameter)

pigmentation

Human hairs are usually one color along the length and denser towards the cuticle

cuticle

Human scales are flattened narrow

medullary index

Ratio of the diameter of the medulla to the diameter of the entire hair (animals are thicker)

Collecting hair as trace evidence

Photograph in situ; use clean forceps

macroscopic analysis

Seen with a naked eye; length, color, and curliness

microscopic analysis

Determines human or non-human; shows presence of dies, hair, treatments

IRMS

Water and food from a specific location will have the same isotope signature as the region/environment

The longer the hair the more information can be gained