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:
1. Follicle - club shaped structure in the skin
2. 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 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 :
1. Shape
2. Length
3. Diameter
4. Texture
5. 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