HAIR

WHY USE HAIR IN FORENSICS? Hair can easily be left at the crime scene. It can adhere to clothes, carpets, and be transferred to other surfaces. Provide clues to the identification of a suspect. Does not easily decompose. Can provide a history of use and exposure to toxins.

introduction Hair is considered to be trace evidence. Hair can be considered class evidence. --> Without follicle cells it cannot be used to identify an individual Hair can also be considered individual evidence. --> With follicle cells present (DNA analysis can be performed)

Structure of hair Hair consists of two parts: Follicle - club shaped structure in the skin Shaft – exposed part of hair (composed of keratin) --> Made of 3 parts: cuticle, cortex, medulla Keratin – protein that makes hair strong and felxible

Structure of hair Shaft: Cuticle- transparent outer layer of the hair --> Looks like scales Cortex - largest part of the hair shaft --> Contains most of the pigment (melanin) Medulla – center part of the hair shaft

To distinguish between animal and human hair use a Medullary Index diameter of hair’s medulla Medullary Index =------------------------------- diameter of the hair M.I. = <.33 hair is human M.I. =>.5 or more, hair is animal

Animals typically have a large medulla.

Medulla differs among species.

Types of hair Hair can vary in : Shape Length Diameter Texture Color

Hair from different parts of the body Hair varies from region to region on the body of the same person Head hair – circular or elliptical in shape Eyebrows and eyelashes – circular with tapering ends Beard and mustache hair – thick, triangular, and coarse Underarm hair – blunt tip Body hair- blunt tip Pubic hair – oval and triangular

HAIR BETWEEN RACES

Treated hair Hair can be treated in different ways. (e.g. artificial bleaching and sun bleaching) Can determine when hair was last treated. Hair grows at a rate of 1.3 cm/month

Substances in the hair shaft Hair grows out of the skin therefore the chemicals the skin absorbs can be found in the hair. A timeline for exposure can be determined. For example, if the toxin is found 9 cm from the root. 9 cm/1.3 = 7 months

Hair follicle If hair is forcibly removed, entire hair follicle may be present. If this occurs, blood and tissue may be attached. DNA analysis can the provide identification with a high degree of certainty. Hair shaft provides only class evidence.

Forcibly removed Follicle intact Pulled