hair. why use hair in forensics? hair can easily be left at the crime scene. it can adhere to...
Post on 03-Jan-2016
215 Views
Preview:
TRANSCRIPT
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.
INTRODUCTIONHair 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:1. Follicle - club shaped structure in the skin2. 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:1. Cuticle- transparent outer layer of the
hair--> Looks like scales
2. Cortex - largest part of the hair shaft--> Contains most of the pigment (melanin)
3. Medulla – center part of the hair shaft
To distinguish between animal and human hair use a Medullary Index
diameter of hair’s medullaMedullary Index =-------------------------------
diameter of the hair
M.I. = <.33 hair is humanM.I. =>.5 or more, hair is animal
Animals typically have a large medulla.
Medulla differs among species.
TYPES OF HAIR
Hair can vary in :1. Shape2. Length
3. Diameter4. Texture5. Color
HAIR FROM DIFFERENT PARTS OF THE BODY
Hair varies from region to region on the body of the same person
1. Head hair – circular or elliptical in shape
2. Eyebrows and eyelashes – circular with tapering ends
3. Beard and mustache hair – thick, triangular, and coarse
4. Underarm hair – blunt tip
5. Body hair- blunt tip
6. 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
top related