Hair and Fiber

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

1. Smell of the burned fiber 2. On contact with the flame, does the fiber coil or melt? 3. Color and structure of the residue left after the fiber burns

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

1. They are easily transferred from victim to suspect 2.They are often overlooked by a suspect 3. They can be easily collected and stored

The period of active hair growth is called the ... stage.

Anagen

Describe three sources of natural fibers. Provide an example of each type of natural fiber.

Animals hair, fur, webbing, plants seeds and fruit, minerals and fiberglass

Explain why roofers removing old asbestos roofs are more at danger of developing lung cancer than a person who installs asbestos flooring.

Roofers removing old asbestos roofs are more at danger of developing lung cancer than a person who installs asbestos flooring because there is a higher quantity of asbestos in roofs than in floors.

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

Silver

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

All hairs on the head of a person are identical

False

Hair is composed of a protein called cellulose

False

Fibers collected as trace evidence are often considered to be class evidence and not individual evidence. For example, the presence of a white cotton fiber found on a suspect and found on a victim at a crime scene is not enough evi- dence to convict the suspect. Justify this statement

In many cases, a fiber can be identified, but not connected to a specific person, rather just a certain group of fibers

Explain how the inhalation of asbestos fibers can lead to lung cancer.

Inhalation of asbestos fibers can lead to lung cancer because the fibers lodge in the tissue of the lung where their presences causes cells to mutate in a specific way leading to the formation of a cancerous tumor growth.

Silk is a natural fiber produced by the silkworm. How is silk produced by the body of the silkworm?

They produce the fiber in their bodies and form it from a single strand that measures 1 to 2km.

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

Tip of the hair

The cortex may contain pigment granules.

True

The shaft of the hair is considered class evidence in a trial

True

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 hair and not a piece of fiber obtained from an article of clothing? (Choose 2)

a) the presence of a cuticle b) a medullary index of 0.33 or less

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

flattened cross section

The shiny nature of silk can be related to

its ability to refract light

A crime-scene investigator views two small, red fibers. One fiber was obtained from the crime scene off the victim's body, and the other red fiber was removed from the cuff of the suspect's pants. Although the two fibers appear to be from the same fabric, the crime-scene investigator determines that the two fibers are indeed very different. List five other characteristics of the fibers that can be detected under a compound microscope that could be used to dis- tinguish the two red fibers.

kinkiness, curliness that you could see under a microscope. Without a microscope, a person might be able to feel that one fiber is kinkier & stiffer than the other.

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

medulla

Cuticle

outer covering of hair shaft, looks like "roof shingles"

Human hair has which type(s) of cuticle?

pigmented

cortex

pigmented layer inside cuticle

Natural fibers can be harvested from

plants, animals, minerals

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

root

mineral fibers such as asbestos are very durable. These fibers are used in all of the following except

rope

Medulla

runs down center of the hair

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

width of medulla and the width of the hair

Why is hair considered class evidence?

Hair is considered class evidence when the follicle is not attached because the follicle is the part that contains DNA. When the follicle is attached, it is considered individual evidence.

Calculate the medullary index of a hair whose diameter is 110 microns wide and whose medulla measures 58 microns. Is this a human or animal hair?

58/110 = . 53 ( >. 33 so it is an animal)

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

A yellowish tint to the hair

Human hair

Pigmentation is denser towards the cuticle Cannot change colors at random Medulla index is thinner than animals Cuticle scales are flat and narrow (imbricate)

animal hair

Pigmentation is denser towards the medulla Can abruptly change colors (in banded patterns Medulla index is thicker than humans Cuticle scales resemble petals (spinous) or a stack of crowns (coronal)

a characteristic of natural fibers is that they

are affected by microscopic organisms

follicle

club shaped structure embedded in the skin

all of the following are characteristics of a synthetic fiber except:

they do not contain any natural fibers