Transcript Hair

Hair
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Bertino
History of Hair Analysis
1. 1883: Alfred Swaine Taylor and Thomas
Stevenson covered hair in a forensic science
text
2. 1910: Victor Balthazard and Marcelle Lambert
published a comprehensive study of hair
3. 1934: Dr. Sydney Smith, analyzed hairs side
by side
4. Today: chemical tests, neutron activation
analysis, and DNA analysis
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Forensic Science: Fundamentals & Investigations, Chapter 3
The Function of Hair
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Regulates body temperature
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Decreases friction
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Protects against sunlight
Forensic Science: Fundamentals & Investigations, Chapter 3
The Structure of Hair
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A follicle embedded in the skin produces the
hair shaft
Three layers:
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the inner medulla
the cortex
the outer cuticle
Forensic Science: Fundamentals & Investigations, Chapter 3
The Structure of Hair
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Forensic Science: Fundamentals & Investigations, Chapter 3
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Forensic Science: Fundamentals & Investigations, Chapter 3
Cuticles, Cortex, and Medulla
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Forensic Science: Fundamentals & Investigations, Chapter 3
Types of Cuticle
and Cortex
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Cuticle:
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Cortex:
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the outermost layer
over-lapping scales that protect the inner layers
Thickest layer
Contains most of the pigment
Distribution of pigment varies
Usually denser nearer the cuticle
Forensic Science: Fundamentals & Investigations, Chapter 3
Animal Hair
and Human Hair
Spinous
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Coronal
Imbricate
Animals: cuticle scales resemble petals
(spinous) or a stack of crowns (coronal)
Humans: commonly flattened and narrow
(imbricate)
Forensic Science: Fundamentals & Investigations, Chapter 3
Coronal
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Forensic Science: Fundamentals & Investigations, Chapter 3
Spinous
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Forensic Science: Fundamentals & Investigations, Chapter 3
Imbricate
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Forensic Science: Fundamentals & Investigations, Chapter 3
Types of Medulla
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Forensic Science: Fundamentals & Investigations, Chapter 3
Medulla Index—
Animals vs. Humans
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Forensic Science: Fundamentals & Investigations, Chapter 3
Types of Hair
Buckled
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Blunt
Double Medulla
A cross section: circular, triangular, irregular,
or flattened
Shape: influences the curl of the hair
Texture: coarse or fine
Forensic Science: Fundamentals & Investigations, Chapter 3
Types of Hair
Human hair varies on the body
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Head
Eyebrows
Lashes
Mustache
Beard
Underarms
Body hair
Pubic
Forensic Science: Fundamentals & Investigations, Chapter 3
The Life Cycle of Hair
Hair proceeds through 3 stages as it develops:
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Anagen stage:
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Catagen stage:
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hair grows and changes
Telogen stage:
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hair actively grows
cells around the follicle rapidly divide and
deposit materials in the hair
follicle becomes dormant
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Forensic Science: Fundamentals & Investigations, Chapter 3
Treated Hair
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Bleaching
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disturbs the scales on the cuticle and
removes pigment
leaves hair brittle and yellowish
Dyeing colors the cuticle and the cortex
Forensic Science: Fundamentals & Investigations, Chapter 3
Racial
Differences
Broad, racial groups do exhibit some shared
physical characteristics
o But NOT applicable to all individuals in these
groups
Therefore,
o Individual hairs CANNOT be assigned to any
of these groups
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Forensic Science: Fundamentals & Investigations, Chapter 3
Animal Hair
and Human Hair
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Pigmentation:
• animal hair is denser toward the medulla
• human hair tends to be denser toward the cuticle
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Banded Color Patterns:
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possible in animals
not in humans
Medulla: much thicker in animals
Forensic Science: Fundamentals & Investigations, Chapter 3
Using Hair in an
Investigation
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Macroscopic investigations indicate
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Phase contrast microscopy shows
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length
color
curliness
presence of dye or other treatments
Electron microscopes yield yet more detail
Forensic Science: Fundamentals & Investigations, Chapter 3
Using Hair in an Investigation
Note the overlapping scales and the pigment
granules in the cortex
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Forensic Science: Fundamentals & Investigations, Chapter 3
Testing for Substances
in the Hair Shaft
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Chemical tests
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Examining a hair shaft
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timeline for exposure to toxins
Neutron Activation Analysis (NAA)
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presence of various substances
concentrations of substances
Forensic Science: Fundamentals & Investigations, Chapter 3
Testing the Hair Follicle
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Microscopic assessment
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Blood test
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Determine blood type
DNA analysis
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Cost effective and quick
Identification with a high degree of confidence
Forensic Science: Fundamentals & Investigations, Chapter 3
Collection and Preservation
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As a general rule, forensic hair
comparisons involve either head hair or
pubic hair.
The collection of 25 full-length hairs
from all areas of the scalp will normally
ensure a representative sampling of
head hair.
Forensic Science: Fundamentals & Investigations, Chapter 3
Microscopic Assessment
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Preparation
Forensic Science: Fundamentals & Investigations, Chapter 3