Forensics of Hair Analysis

Hair Forensics Hair: Can demonstrate physical contact with Person Place Object

Hair Facts Grows from the papilla…but past that, it’s dead cells and protein – no DNA A shaft projects above the skin, and a root that is imbedded in the skin

Hair: Components Keratin (a protein) Melanin (a pigment) Trace metals Deposited in the hair during its growth Absorbed from the external environment. After a period of growth, the hair remains in the follicle in a resting stage to eventually be sloughed from the body.

Basic Hair Structure

Hair Cuticle Translucent outer layer of the hair shaft consisting of scales… … always point from the root end of the hair to the distal or tip end of the hair.

Cuticle There are three basic scale structures that make up the cuticle Combinations and variations of these types are possible. Imbricate, Flattened Spinous, Petal-like Coronal, Crown-like

Bat Hair and Mink Hair

Human Hair Imbricate or “flattened” scales show overrlapping scales with narrow margins. Can show on many animal hairs.

Medulla The medulla is a central core of cells that may be present in the hair. Human Animal Deer

Medulla When present in human hairs: Generally less than 1/3 the diameter of the hair shaft. In animal hairs: Normally continuous Generally more than 1/3 the diameter of the hair shaft.

Animal vs. Human Hairs Human hairs Animal hairs Color consistent the length of the shaft Pigmentation evenly distributed, or slightly more dense toward the cuticle Animal hairs May exhibit radical color changes in a short distance, called banding. The pigmentation is more centrally distributed, perhaps although more dense toward the medulla.

Hair Forensics: DNA Often it is not possible to extract DNA fully, or there is not enough tissue present to conduct an examination. DNA examinations destroy hairs, eliminating the possibility of further microscopic examination.

Forensic Identification Human hairs can generally be identified by racial origin and body area. Racial indicators apply primarily to head hairs.

Caucasian African-American Mongoloid - Asian

Where is this hair from? Certain features of individual hairs identify the region of the body where it originated.

Where is this Hair from? Limb

Where is this hair from? Beard triangular in cross-section

Things to consider when viewing hair Length: May have been cut May vary considerably within the individual Tip: May be affected by grooming and hygiene

Glass-Cut or Broken Hair Tip Cut Hair Tip Worn or Razor-Cut Tip

Dyed hairs possess an unnatural cast or color Dyed hairs possess an unnatural cast or color. In addition, the cuticle will take on the color of the dye

Scissor Cut Razor Cut Broken Hair Burned Hair

What is this?

Joann