Forensic Analysis of Hair

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Forensic Analysis of Hair
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How useful is hair in a forensic investigation?

• Used to back up circumstantial evidence and help
  place individuals at the crime scene.
• Hair without the follicle class characteristics
• Hair with the follicle individual
  characteristics (allows for DNA fingerprinting)

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Morphology of Hair
Morphology - refers to color and structure

• Hair grows out of an organ called the hair
  follicle
• the root is embedded in the follicle
• the shaft is the main part of the hair
• the tip is at the opposite end to the root.

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Morphology of Hair

• Forensic scientists primarily examine the hair
  shaft, which is composed of three layers
• a. Cuticle b. Cortex c. Medulla

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Cuticle

• Outer surface of hair
• Reason that hair resists
• changes in structure and
• does not easily decompose
• Formed from overlapping scales that point towards
  the tip of the hair (formed from keratinized
  cells)
• Scales are more prominent on animal hair than
  human hair and can be used to ID the species
• Examined by comparison microscope or hair casts.

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Examples of Cuticles
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Cortex

• Main body of hair shaft
• Contains pigment granules
• and possibly air bubbles
• called cortical fusi
• Color, shape and distribution of granules are
  analyzed by criminalist
• Examined by placing hair on a microscope slide in
  a liquid with a similar refractive index

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Medulla
Central canal running through the hair (not
always present)

• Medullary index diameter of the medulla
  relative to diameter of entire hair (represented
  as a fraction)
• Humans approx. 1/3 or less
• Other animals 1/2 or more

• 0 1/10 1/3 1/2 9/10

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Medulla Classification
Human usually absent or fragmented - can be
continuous (Mongoloid) Animal usually
continuous or interrupted -many are also
patterned (ex, cat string
of pearls) -A database has been established
containing the 35 most common types of animals
encountered. Can be searched by scale pattern
or medulla type
Also Absent Patterned
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Examples of Medullas
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Hair Shape
Straight Curly
Kinked Asian/ Caucasian
African Caucasian No twist No twist
Twists and undulates
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Root
Allows for hair growth
3 Stages of hair growth 1. anagen (up to 6
years) follicle is actively producing
hair - roots have a flame-shaped appearance
b/c attached to the follicle - if
the hair is pulled out at this stage, typically
will have the follicular tag attached 2.
catagen (2-3 weeks) hair growing still but
slowly - roots have elongated appearance b/c
root bulb shrinks 3. telogen (2-6 months)
hair pushed out of follicle and shed -
root has a club shaped appearance
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Stages of Hair Growth
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Identification and Comparison of HairSteps the
Forensic Analyst Takes

• Determine if hair belongs to an animal or a
  human
• EASY use medulla/cuticle to ID species

• Determine if human hair matches known samples
• HARD morphology/color differs w/in the same
  person

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Things examined by the forensic scientist

• Compare color, length, diameter
• Examine medulla, cuticle, cortex
• abnormal morphology can indicate disease or
  vitamin deficiencies
• 3. Try to determine if hair is dyed or bleached
• a. Dyed hair dye reaches into the cortex and
  cuticleb. Bleached hair removes pigment so
  has yellow tint
• Estimate time of dying possible since hair grows
  about 1cm/month

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Common Questions

1. Can the area of the body the hair came from be
   determined?

2. Can racial origin, age and sex be determined?

• Racial origin usually can be determined
• African American kinky, dense, unevenly
  distributed pigments
• Caucasian straight or wavy, more evenly
  distributed pigments

Age and sex cannot be determined at this time

1. Can it be determined if hair was removed with
   force or naturally shed?

• Typically hair removed by force or with a brush
  has follicle still attached
• Important consideration is how quickly hair is
  pulled out

4. Are there any ways to individualize hair?

• DNA technology examining follicular tag or root
  when hair is in anagen phase

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Collection of Hair

1. Need an adequate number of control samples from
   same area of body

2. Need to try and collect full length hairs
from all over scalp

1. Entire hair length should be collected since may
   change in color and morphology

4. During an autopsy it is now routine to remove
hair samples in case they are needed later
on.
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Case Story
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Recap of Analytical Techniques
Comparison microscope Physical Properties
Temperature (melting point/freezing
point) Weight/Mass Density Refractive
Index Chemical Properties Color
tests Microcrystalline tests Chromatography Spe
ctrophotometry Mass Spectrometry
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Objectives

• Learn the morphology and distinguishing features
  of hair
• Compare various different types of hair under a
  microscope.
• Analyze the medulla, cortex and cuticle of
  several hair samples.
• Describe the hairs of several species of
  animals.
• 5. Describe the collection procedures for hair.