History of Hair Analysis - Mrs. Sikes

[Pages:27]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

o Regulates body temperature o Decreases friction o Protects against sunlight

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Forensic Science: Fundamentals & Investigations, Chapter 3

The Structure of Hair

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Forensic Science: Fundamentals & Investigations, Chapter 3

The Structure of Hair

o A follicle embedded in the skin produces the hair shaft

o Three layers (illustrated above):

? the inner medulla ? the cortex ? the outer cuticle

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Forensic Science: Fundamentals & Investigations, Chapter 3

Biology of Hair

Hair is composed of the protein keratin, which is also the primary component of finger and toe nails.

Hair is produced from a structure called the hair follicle. Humans develop hair follicles during fetal development, and no new follicles are produced after birth.

Hair color is mostly the result of pigments, which are chemical compounds that reflect certain wavelengths of visible light.

Hair shape (round or oval) and texture (curly or straight) is influenced heavily by genes. The physical appearance of hair can be affected by nutritional status and intentional alteration (heat curling, perms, straightening, etc.).

The body area (head, arm, leg, back, etc.) from which a hair originated can be determined by the sample's length, shape, size, color, and other physical characteristics.

In order to test hair evidence for DNA, the root must be present.

Sources: & (Hairs)

Hair Structure

Hair is composed of three principal parts: Cuticle ? outer coating composed of overlapping scales

Cortex ? protein-rich structure around the medulla that contains pigment

Medulla ? central core (may be absent)

The structure of hair has been compared to that of a pencil with the medulla being the lead, the cortex being the wood and the cuticle being the paint on the outside.



Cuticles, Cortex, and Medulla

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Forensic Science: Fundamentals & Investigations, Chapter 3

Types of Cuticle and Cortex

o Cuticle:

? the outermost layer

? over-lapping scales that protect the inner layers

o Cortex:

? Thickest layer

? Contains most of the pigment

? Distribution of pigment varies

? Usually denser nearer the cuticle

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? Made up of keratin

Forensic Science: Fundamentals & Investigations, Chapter 3

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