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Chapter 3
Forensics: The Study of Hair
| Question | Answer |
|---|---|
| What types of evidence is hair considered to be? | trace evidence and class evidence |
| What are the characteristics of hair? | can be easily left behind, secondary transfer, does not easily decompose, offers clues to racial background, chemical tests, and DNA |
| What are the functions of hair? | protects skin, regulates body temperature, decreases friction, and acts as a sense organ |
| What is Keratin? | a protein produced in the skin that makes the hair strong and flexible |
| What does the sebaceous gland do? | secretes oil and helps to keep the hair conditioned |
| What is the hair follicle? | structure in the skin |
| What is does the papilla do? | contains the blood vessels that supply the nutrients to feed the hair and help it grow |
| What is the hair shaft? | it is the outer part of the hair and is made up of keratin |
| What are the three layers of the hair shaft? | cuticle, cortex, and medulla |
| What is the cuticle? | outside layer of the hair shaft |
| What is the function of the cortex and where is it located? | inside; part pf the hair that gives the hair its color |
| What are characteristics of the medulla? | runs through the center and can be hollow or filled with cells |
| How can hair vary? | shape, length, diameter, texture, and color |
| Head hair | circular or elliptical cross section |
| Eyebrows and eyelashes | circular w/ tapered ends |
| Beard hair | thick and triangular/coarse/double medulla |
| What happens with treated hair? | bleached hair removes pigment and gives hair a yellow color, disturbs the scales on the cuticle, changes the color of the hair shaft, and the cuticle and cortex take on the color of the dye |
| Animal hair | pigment is denser towards the medulla, banded color patterns, and a thicker medulla |
| Human hair | pigment is denser towards the cuticle, no banded color patterns, and is usually one color |
| How are hair samples collected during an investigation? | plucked, shave, scrapping, placing tape over the surface so that hair sticks to it, and vacuum large surfaces |
| Anagen | lasts 1,000 days, 80-90% of human hair is in this stage, active growth |
| Catagen | 2%, hair grows and changes/turns grey |
| Telogen | 10-18%, hair follicle is dormant, hair is easily lost |
| Macroscopically viewing a hair sample | hair length, color, and curliness |
| Microscopically viewing a hair sample | pattern of the medulla, pigment of the cortex, and types of scales on the cuticle |
| Fluorescence microscope | can detect dyes and hair treatments |
| Why is a hair follicle important? | blood and tissue attached to the follicle can be analyzed and DNA analysis |
| How can you test for substances in the hair shaft? | hair grows out of the skin and the chemicals that the skin absorbs can become incorporated in the hair and chemicals/toxins/drugs can be detected |
Created by:
margaret_05
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