Hair
Cuticle
Cortex
Follicle
Hair
Root
root
1
Hair growth
Anagen phase
Growth phase
Anagen phase
Up to 6 years
Hairs pulled out will
contain DNA in the root
2
Hair growth
Growth phase slows and stops
Catagen phase
Transitional phase
Catagen phase,
2 to 3 weeks
3
Hair growth
Growth stops and root shrivels
Hair can fall out
Telogen phase
Telogen phase,
Do not contain much DNA
2 to 6 months
4
Cross-section of Hair
Looks scaly
Cuticle
Useful for species
Medulla
identification
Width & pattern
Cortex
is characteristic
of species
Contain pigment
granules
May not be
continuous
Colour, size,
distribution, density
5
Human or animal hair?
Dog cuticle
Cat cuticle
Human
cuticle
6
Human or animal hair?
Human
Dog medulla Cat medulla
medulla
7
Individualisation
Follicle tissue may
contain DNA attached
to forcibly removed hair
If not enough DNA Rely on comparison
8
Individualisation
Hair from crime scene
Hair from a person Suspect or corpse
Compare hairs under a microscope
FBI survey 11% wrong
9
Hair analysis
Hair
Contains a record of chemicals
that were in your body in the past
10
Hair analysis
E.g. bar raid
Someone tested positive for ketamine
Denied being a drug user
during police questioning
11
Hair analysis
Hair sample
Cut off at the scalp (newest hair)
Cut hair into segments
Analyze the segments
12
Hair analysis
If person telling the truth
No ketamine in the hair
If ketamine found evenly distributed along hair
Person was lying
Habitual user
13
Hair analysis
Helps us determine chemical exposure
Willingly exposed
Unknowingly exposed
14
August, 1991
Robert Curley died in hospital
Analysis of body fluids High levels of thallium
Worked in a University Chemistry lab
Exposure to thallium?
15
August, 1991
Low levels of thallium
In wife, daughter and his thermos flask
$297 000 insurance
Body exhumed Hair analysis
16
Hair analysis
Longest hairs were about 10 months old
Thallium exposure
for over 9 months
Spike in thallium levels
just before his death
Hair analysis
17