AIM: How is hair analyzed in
forensics?
Do Now: A single scalp hair approximately 14
inches long was found on a female victim of African
descent who lives alone. The hair had a low
distribution of phenomelanin in the cortex, a slightly
oval cross section, and a medulla that was
fragmented. What might the person that police wish
to question look like?
HW: complete questions on back of hair analysis lab
AIM: How is hair analyzed in
forensics?
Do Now: Compare the layers of a pencil to the
layers found in hair. What would the paint
represent? The wood? The lead?
HW: Textbook Read pages 201-204. Write out and
answer each bold faced question on hair identification
What are the parts of a hair strand?
• 1. Root/bulb
• Embedded in hair follicle
• 2. Shaft
• Composed of 3 layers
–Cuticle
–Cortex
–Medulla
• 3. Tip
• Where the hair strand ends
How can you determine different
types of hair by analyzing the
medulla?
Medulla
• 3 types of medulla found in human hairs
– I.Continuous - most East Asian scalp hairs + pubic hair
– II.Fragmented –
Most human scalp hairs other than
– III.AbsentEast Asian
Continuous Medulla Fragmented Medulla
Absent Medulla
Solid canal
throughout hair
No Medulla Found
Interrupted canals
throughout hair
Root of Hair
• Provide the tools to produce hair and continue its
growth
• 3 Stages of Growth (different looking roots)
– Anagen -initial phase may last up to 6 years, root is
flame shaped
– Catagen –transition phase (2-3 weeks), root is
elongated
– Telogen –phase where hair naturally falls out of the
skin, root is club-shaped
How could Fajardo Aceves Jesus
Manuel remove his hair
Why is hair analysis so important?
• We lose and replace about 100 hairs per
day.
• It’s likely that we left a strand of hair in
everyplace we traveled to yesterday
Why are hairs collected for drug tests?
• Materials that come into the body can be
delivered by blood to hair follicle
• Material can be deposited in cortex of hair
Why are hair follicle drug tests becoming widely
used?
• Drugs and their metabolites can be detected over
longer periods of time than blood, urine, or saliva tests
• Since hair grows about 1cm (½ inch) a month, we can
get a timeline of when drug use
• We can see how often person uses drugs (every week
or once in the last 3 months)
Tuesday
Substance
Urine
Hair
Blood/Saliva
Alcohol
6–24 hours
up to 2 days
12–24 hours
Methamphetamine
3 to 5 days
up to 90 days 1–3 days
MDMA (Ecstasy
24 hours
up to 90 days 25 hours
Cannabis
3 to 7 days, up
to >30 days
after heavy use
and/or in users
with high body
fat
up to 90 days 2–3 days in blood,
up to 2 weeks in
blood of heavy
users. Saliva for
Cocaine
2 to 5 days
up to 90 days 2 to 5 days
Cotinine (a break-down
product of nicotine)
2 to 4 days
up to 90 days 2 to 4 days
Heroin
3 to 4 days
up to 90 days 1– 2 days
LSD
24 to 72 hours
up to 90 days 0 to 3 hours
2–6 hours
What other materials can be traced in hair?
• Poisoning by heavy metals (Arsenic, Mercury,
lead)
• Dietary deficiencies (low vitamin and mineral
levels)
What is a drawback to hair testing?
• Scalp oils coat the cuticle of the hair and sometimes
capture materials from environment Ex: crack smoke
in car
• Can cause “false positives”
• Scientists must be careful to examine only the cortex
of the hair
http://www.youtube.com/watch?v=
GPrYZ9wwCv4
• http://www.cbsnews.com/video/watch/?id=
7253008n