Forensic Science Ch 3+4 Hair and Fiber

*True or False* All hairs on the head of a person are identical.

False; Different

*True or False* Hair is composed of a protein called cellulose.

False; Keratin

Why is hair considered class evidence?

Hair is considered class evidence because it cannot be used to identify specific individuals

*A fiber is collected at a crime scene. When viewed under a compound microscope, what two traits would indicate that the fiber was a human and not a piece of fiber obtained from an article of clothing?*

If the medullary index was .33 or less and had a presence of a cuticle.

The hair shaft is composed of the cuticle, cortex, and...

Medulla

*Describe the structure of hair. Include ( follicle, medulla, cortex, and cuticle)*

The hair is consists of two parts: a *follicle* and a shaft. A follicle is a network of blood vessels that supply nutrients. The hair shaft is made up of three layers: an inner *medulla*, a *cortex*, and an outer *cuticle*. The cuticle is the outer coating composed of overlapping scales. The cortex is a protein-rich structure containing pigments. The medulla is the central core and it may be absent.

*How is hair collected from a suspect?*

They gather about 25-50 hair sample per a woman pulled and not cut to get the follicle to test the DNA.

*True or False* The cortex may contain pigment granules.

True

*True or False* The shaft of the hair is considered class evidence in a trial.

True

A characteristic of natural fibers is that they...

are affected by microscopic organisms

Which of the following characteristics is found in typical Asian hair?

dark medulla

Human hair has which type(s) of cuticle?

imbricate

The shiny nature of silk can be related to

its ability to refract light

Natural fibers can be harvested from

plants, animals, and minerals

Which part(s) of a hair can be analyzed for DNA?

root

Mineral fibers such asbestos are very duable. These fibers are used in all the following what?

shingles, floor tiles, and break liners

Neutron activation analysis can check hair for the presence of....

silver

Which of the following observations are used to help identify a specific fiber?

the smell of burned fiber, on contact with the flame, and color and structure of the residue left after the fiber burns

Fibers are an excellent source of trace evidence because...

they are easily transferred from victim to suspect, they are often overlooked by a suspect, and they can be easily collected and stored.

What are the following characteristics of a synthetic fiber?

they are formed by combining monomer compounds into polymer molecules, they are man made and they are used in the production of carpet fibers

The cuticle scales of the hair always point toward the...

tip of the hair

Which factors are used to calculate the medullary index of the hair?

with of medulla and width of hair

Which of the following is most likely a result of hair bleaching?

a yellowish tint to the hair

The period of active hair growth is called the ___________ stage

anagen

Although variations can occur, which of the following best describes northern European hair?

straight with evenly distributed granules

What characteristics of cotton make it a great source of fiber for clothing?

the fibers are easily woven and dyed