Transcript Chapter 3 The Study of Hair, Hair Analysis

Drill
• Name a function of hair.
• What are the three parts of a hair strand?
• Name and describe the 5 types of
medullary patterns of hair.
Chapter 3 The Study of Hair,
Hair Analysis
Identification of species through
microscopy.
Chapter 3 The Study of Hair
• identify the various parts of a hair
• describe variations in the structure of the
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medulla, cortex, and cuticle
distinguish between human and nonhuman hair
determine if two examples of hair are likely to be
from the same person
explain how hair can be used in a forensic
investigation
calculate the medullary index for a hair
History of Hair Analysis
Alfred Swaine Taylor and Thomas Stevenson,
in 1883, wrote a forensic science text that
included a chapter on hair.
2. Victor Balthazard and Marcelle Lambert, in
1910, published a comprehensive study of
hair.
3. Dr. Sydney Smith, in 1934, first used a
comparison microscope to analysis hairs side
by side.
4. Advances continue today with chemical tests,
neutron activation analysis, and DNA analysis.
1.
The Function and
Structure of Hair
• Hair on mammals helps to regulate body temperature,
decrease friction, and protect against sunlight.
• Hair consists of (a) a hair shaft produced by (b) a
follicle embedded in the skin.
• A hair has three layers (illustrated above): the inner
medulla, the cortex, and the outer cuticle.
Review
• Name a function of hair.
• Name the three layers of hair.
• What kind of analysis can be done with
hair?
Types of Cuticle and Cortex
The Outer 2 Layers
The Cuticle is the outermost layer made of over-lapping
scales that protect the inner layers of the hair.
The Cortex is the thickest layer containing most of the
pigment giving hair its color.
 The distribution of pigment in the cortex varies from
person to person.
 Pigment, commonly, is denser nearer the cuticle.
Types of
Medulla
The medulla (the inner section) can be
hollow or filled, absent, fragmented,
continuous, doubled, pigmented, or unpigmented.
Examination of the Medulla
Review
• What is the purpose of a cuticle?
• What in the cuticle can vary from person to
person that gives a variety of hair color?
• Name and describe two medullas.
Types of Hair
• The cross section of a hair can be circular, triangular,
irregular, or flattened influencing the curl of the hair.
• The texture of a hair can be coarse or fine.
• Different regions of the body on which hair can vary are
(1) head, (2) eyebrows and lashes, (3) mustache and
beard, (4) underarms, (5) overall body (auxiliary hair),
and (6) pubic.
The Life Cycle of Hair
Hair proceeds through 3 stages as it develops:
1. During the long anagen stage, hair actively
grows. The cells around the follicle rapidly
divide and deposit materials in the hair.
2.
In the catagen stage, the hair grows and
changes.
3.
Hair is in the telogen stage when the follicle
becomes dormant. During this stage, hairs
easily can be lost.
Treated Hair
Forensic investigators sometimes can link hair
from a location with an individual.
– Bleaching disturbs the scales on the cuticle and
removes pigment leaving hair brittle and a
yellowish color.
– Dyeing colors the cuticle and the cortex of the
hair shaft.
Because of this and because hair grows daily, a
person’s treated hairs will have specific characteristics in common with her or his lost hairs.
Review
• Name three regions that hair can be from
on humans.
• Name and describe the three stages of
hair growth.
• What is unique about treated hair that can
aid forensics investagators?
Racial
Differences
• Hair examiners have identified some physical
characteristics that generally can be associated with
broad, racial groups.
• These characteristics, however, will not apply to all
individuals in these groups.
• In addition, at times, it will be impossible to assign
specific hairs to any of these groups be-cause their
characteristics are poorly defined or hard to measure.
Human Hairs
• Racial Determination
Negroid
Mongoloid
Caucasian
Hair Roots
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Pulled
Forcibly Removed
Shed
Animal Hair and Human
Hair
Core: the medulla -- Thickest layer: the cortex - Outermost: the cuticle
• Pigmentation in animal hair is denser
toward the medulla. In Humans it tends to
be denser toward the cuticle.
Unlike human hair, animal hair abruptly
can change colors in banded patterns.
• The medullary index is different. In
animals the medulla is much thicker than it
is in humans.
Patterns in Animal Species
Examination of Scale Pattern
• Is it possible to tell the difference between
human hair and animal hair? If YES
explain.
• How does a pulled root look different from
a root that sheds?
Animal Hair and Human
Hair
Spinous
Coronal
Imbricate
The outermost layer of the hair shaft (the cuticle), is typically
different in animals and humans.
– The cuticle scales in animals tend to resemble petals
(spinous) or they give the appearance of a stack of crowns
(coronal).
– The cuticle scales in humans commonly are flattened and
narrow (imbricate).
Tip of the Shaft
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Burned
Cut
Razored
Split
Review
• How does a cuticle differ between animals
and humans?
• Named and describe two types of hair
shafts.
Collection of Hair Specimen
Using Hair in an
Investigation
• Macroscopic investigation can indicate length,
color, and curliness.
• Microscopic investigation can indicate fine
detail in hair structure.
– Phase contrast microscopy, for example,
can show the presence of dye or other
treatments.
– Electron microscopes can provide more
detail of the surface or interior of the sample.
In the sample above, note the overlapping
scales and the pigment granules in the cortex.
Testing for Substances in
the Hair Shaft
1.
Chemicals that the skin absorbs often can be
detected by analysis of the hair shaft.
2.
A forensic scientist can perform chemical tests
for the presence of various substances.
3.
The hair shaft can be examined in sections to
establish a timeline for exposure to toxins.
4.
Neutron Activation Analysis (NAA) can
determine concentrations of substances in the
sample.
Testing the Hair Follicle
Microscopic assessment of the follicle is
performed first because it is cost effective and
quick.
– If a microscopic match is found, the follicle
can be blood tested and perhaps show the
blood type.
– If a microscopic match is found, the follicle
can be DNA analyzed to provide identification
with a high degree of confidence.
Review
• Name two types of investigations that can
be done with hair and how are they
different?
. . . . . . . . . . . . . . . . . Summary
• Hair consists of a (a) hair shaft produced by a
(b) follicle embedded in the skin.
• The shaft consists of an outer cuticle, a cortex,
and an inner medulla.
• Various hair treatments produce characteristic
effects useful to forensic experts.
• Some characteristics allow them to be grouped
into general racial categories.
• Forensic experts examine hair using
chemicals, light, electrons, neutrons, and DNA
sequencing.