Forensic Lab
Investigations
Hair Analysis
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What Is Hair?
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Produced by hair follicle
Consists of:
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Shaft (projects from skin) and a root (embedded in
the follicle)
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Shaft is flat and ribbon-like in cross-section – curly hair
Oval shaft – wavy hair
Round shaft – straight hair
Hair Analysis
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Three layers of protein:
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Medulla – center section made of large cells
separated by air spaces
Cortex – surrounds medulla; bulky with
several layers of flattened cells
Cuticle – outermost layer, looks like shingled
roof
Greatest source of strength
 Contains pigments – small, dark, and solid
structures that are granular in appearance
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Hair Analysis
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Hair Types:
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Scalp – uniform
Beard – coarse, curved
Eyebrow, nose, ear, eyelid – shorter and stubbier,
wide medullas; taper at end
Axillary – uneven pigments; fine point at end
How did it come out?
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Fell out – bulblike root
Pulled out – sheath attached to bulb or mutilated
appearance
Scale Pattern: Human Hair
Hair Analysis
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Hair Identification: Animal Versus Human Hairs
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Pigmentation
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Human Hairs are consistent in color and pigmentation
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Animal hairs exhibit radical color changes
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Pigmentation is more centrally distributed, more dense toward the
medulla
Medulla
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Pigmentation is evenly distributed, or slightly more dense toward the
cuticle
In human hairs, has a width that is generally less than onethird the overall diameter of the hair shaft
In animal hairs, generally occupies an area of greater than
one-third the overall diameter of the hair shaft
Root
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Human hairs roots commonly club-shaped
Animal hairs roots highly variable
Pigment in Animal Hair
Human Hair: Root
Hair Analysis
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Microscopic Examination
Why Examine?
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Decays slowly compared to tissues and fluids
May have to compare hundreds of samples
Indicate physical contact
Hair Analysis
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What information can a forensic scientist obtain
from a hair sample?
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The source (human or animal)
The age
Hair pulled out or fell out
Treatment of hair
Indicates if bleached or dyed
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Dyed have less prominent pigment granules
Hair grows about ½ inch per month
What part of body
Drugs, soil, lice
DNA analysis
Human Hair: Brown vs. Red
Human Hair Types
Limb Hair versus
Facial Hair
Differences in Hair
Hair Cut Types:
Rounded
Cut
Broken
Worn Razor
Abraded
Dyed Hair