Chapter 3 The Study of Hair B y 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

In the beginning....

Fish Amphibians Reptiles Insects Mammals...have hair! Cold Blooded Warm Blooded...and then there were... Evolution is a process of change...it does not say how we got here...

Hair is good because... ·it insulates (helps regulate body temp) ·decreases friction ·protects skin from sunlight ·acts as a sense organ The Function of Hair

·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. The Structure of Hair

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 un- pigmented.

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.

Treated Hair · 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...S0...Forensic investigators sometimes can link hair from a location with an individual.

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.

Racial Differences

Animal Hair and Human Hair ·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. Deer Hair Human Hair

Animal Hair and Human Hair 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). Deer Hair Human Hair

Hair is class evidence...not individual evidence!