1. Chapter 3 The Study of Hair By the end of this chapter you will be able to:
identify the various parts of a hair
describe variations in the structure of the 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
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Forensic Science: Fundamentals & Investigations, Chapter 3

2. History of Hair Analysis
Alfred Swaine Taylor and Thomas Stevenson, in , wrote a forensic science text that included a chapter on hair.
Victor Balthazard and Marcelle Lambert, in 1910, published a comprehensive study of hair.
Dr. Sydney Smith, in 1934, first used a to analysis hairs side by side.
Advances continue today with , neutron activation analysis, and .
Forensic Science: Fundamentals & Investigations, Chapter 3

3. The Function and Structure of Hair
Hair on mammals helps to , decrease friction, and .
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 , the , and the outer .
Forensic Science: Fundamentals & Investigations, Chapter 3

4. Types of Cuticle and Cortex The Outer 2 Layers
The Cuticle is the outermost layer made of over-lapping that protect the inner layers of the hair.
The Cortex is the thickest layer containing most of the giving hair its color.
The of pigment in the cortex varies from person to person.
Pigment, commonly, is denser nearer the cuticle.
Forensic Science: Fundamentals & Investigations, Chapter 3

5. Types of Medulla
The medulla (the section) can be hollow or filled, absent, fragmented, continuous, doubled, pigmented, or un- pigmented.
Forensic Science: Fundamentals & Investigations, Chapter 3

6. Types of Hair Buckled Blunt Double Medulla
The cross section of a hair can be circular, triangular, irregular, or flattened influencing the curl of the hair.
The of a hair can be coarse or fine.
Different regions of the 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.
Forensic Science: Fundamentals & Investigations, Chapter 3

7. The Life Cycle of Hair Hair proceeds through as it develops:
During the long stage, hair actively grows. The cells around the follicle rapidly divide and deposit materials in the hair.
In the stage, the hair grows and changes.
Hair is in the stage when the follicle becomes dormant. During this stage, hairs easily can be lost.
Forensic Science: Fundamentals & Investigations, Chapter 3

8. Treated Hair
Forensic investigators sometimes can link hair from a location with an individual.
Bleaching disturbs the scales on the cuticle and leaving hair brittle and a yellowish color.
Dyeing the cuticle and the cortex of the hair shaft.
Because of this and because hair , a person’s treated hairs will have specific char- acteristics in common with her or his lost hairs.
Forensic Science: Fundamentals & Investigations, Chapter 3

9. Racial Differences
Hair examiners have identified some that generally can be associated with broad, racial groups.
These characteristics, however, will not apply to 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.
Forensic Science: Fundamentals & Investigations, Chapter 3

10. 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 than it is in humans.
Forensic Science: Fundamentals & Investigations, Chapter 3

11. 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 ( ) or they give the appearance of a stack of crowns ( ).
The cuticle scales in humans commonly are flattened and narrow ( ).
Forensic Science: Fundamentals & Investigations, Chapter 3

12. Using Hair in an Investigation
Macroscopic investigation can indicate .
Microscopic investigation can indicate .
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.
Forensic Science: Fundamentals & Investigations, Chapter 3

13. Testing for Substances in the Hair Shaft
Chemicals that the often can be detected by analysis of the hair shaft.
A forensic scientist can perform chemical tests for the presence of various substances.
The can be examined in sections to establish a timeline for exposure to toxins.
Neutron Activation Analysis (NAA) can determine in the sample.
Forensic Science: Fundamentals & Investigations, Chapter 3

14. Testing the Hair Follicle
Microscopic assessment of the follicle is because it is cost effective and quick.
If a microscopic match is found, the follicle can be and perhaps show the blood type.
If a microscopic match is found, the follicle can be to provide identification with a high degree of confidence.
Forensic Science: Fundamentals & Investigations, Chapter 3

15. 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.
Forensic Science: Fundamentals & Investigations, Chapter 3