Forensics Chapter 4 – Flashcards

without a defined shape; fibers composed of loose arrangement of polymers that are soft, elastic, and absorbing (ex. cotton)

regularly shaped; fibers composed of polymers packed side by side, which make it stiff and strong (ex. flax)

the passing of evidence, such as a fiber, from victim to suspect or vice versa

the smallest indivisible bit of a textile, it must be at least 100 times longer than wide

a collection of mineral crystals formed into a recognized pattern

a small molecule that may bond to other monomers to become a polymer

a fiber produced naturally and harvested from animal, plant, or mineral sources

a substance composed of long chains of repeating units

a fiber made from a man-made substance such as plastic

the transfer of evidence such as a fiber from a source (ex. carpet) to a person (suspect), and then to another person (victim)

a flexible, flat material made by interlacing yarns (or "threads")

fibers that have been spun together

1. Fiber- the smallest indivisible unit of a textile, it must be at least 100 times longer than wide 2. Yarn- fibers that have been spun together 3. Textile- a flexible, flat material made by interlacing yarns (or "threads")

Fibers are considered trace evidence because these fibers may have fallen from a victim to suspect or suspect to victim.

1. Direct Transfer-the passing of evidence, such as a fiber, from victim to suspect or vice versa 2. Secondary Transfer- the transfer of evidence such as a fiber from a source (ex. Carpet) to a person (suspect), and then to another person (victim)

It is important to collect fibers evidence quickly because within 24 hours, an estimated 95% of all fibers may have fallen from victim or been lost from the crime scene.

95% of fibers fall off of person in the first 24 hours

The number of fibers found at a crime scene might affect the type of testing that the investigators can perform because if you only have one fiber from a crime scene you cannot do tests that may damage or alter the fiber in anyway. If you have multiple fibers you can do test such as burning the fiber or dissolving in various liquids.

The types of testing that can be taken place with a large number of fibers are burning a piece of the fiber and dissolving in various liquids.

1. Natural Fibers 2. Synthetic Fibers

1. Animal Fibers- provides fibers from 3 sources: hair, fur, and webbing. Made of proteins. Used in clothing, carpets, and decorative hangings such has curtains and bedding. (Ex. Curtains, bedding, clothing, heavy coats, carpets, bags, furniture upholstery, and silk. 2. Plant Fibers- Grouped by the part of the plant from which they come. Seeds, fruits, stems, and leaves all produce natural fibers. Characteristics vary greatly; some are very thick and stiff whereas others are very smooth, fine, and flexible. Often short and become brittle over time. (ex. Cotton) 3. Stem Fibers- Hemp, jute, and flax are all produced from a plants stem. They do not grow as single, unconnected fibers like cotton but in bundles. Bundles maybe 6 feet in length and extend the entire length of the plant. (ex. Linen) 4. Mineral Fibers- are neither protein nor cellulose. Fiberglass is a fiber form of glass. Its fibers are very short, very weak, ad brittle. Fibers are very fine and easily stick to the skin, causing an itchy rash on the skin. (Ex. Insulation) Asbestos is a mineral naturally occurring in different typed of rice with crystalline structure composed of long, thin fibers. Very durable. (Ex. Brake lining, ceiling tiles, floor tiles, fire-resistant clothing, and shingles)

Wool might smell like burnt hair when on fire because wool is made from animal hair.

1. Regenerated Fibers- derived from cellulose and are mostly plant in origin (Ex. Rayon) 2. Synthetic Polymer Fibers- originate with petroleum products and are non-cellulose-based fibers. Man-made polymers that serve no other purpose except to be woven into textiles, ropes, and the like. (Ex. Rope)

1. Polyester- very common synthetic fiber represents a very large group of fibers with a common chemical makeup. Found in polar fleece, wrinkle-resistant pants, and is also added to many natural fibers to provide additional strength 2. Nylon- has properties similar to polyester, except it is easily broken down by light and concentrated acid. Was first introduced as artificial silk, and synthetic pantyhose still go by the name nylons. 3. Acrylic- often found as an artificial wool or imitation fur, acrylic has a light fluffy feel. Acrylic clothing tends to ball or pill easily. This is an inexpensive fiber. 4. Olefins- are used in high performance clothing, such as thermal socks and carpets, because they are very quick drying an resistant to wear.

1. Plain- alternating warp and weft threads. Firm and wears well, snag resistant, low tear strength, and tends to wrinkle. 2. Basket-Alternating pattern of two weft threads crossing two warp threads. An open or porous weave, does not wrinkle, not very durable, tends to distort as yarns shift, and shrinks when washed. 3. Satin- one weft crosses over three or more warp threads. Not durable, tends to snag and break during wear, shiny surface, high light reflectance, and little friction with other garments. 4. Twill- Weft is woven over three or more warps and then under one. Next row, the pattern is shifted over on to the left or right by one warp thread. Very strong, dense and compact, different faces, diagonal design on surface, and soft and pliable. 5. Leno- this uses two warp threads and a double weft thread. The two adjacent warp threads cross over each other. The weft travels left to right and is woven between the two warp threads. Open weave, easily distorted with wear and washing, and stretches in one direction only.

Thread Count- the number of threads that are packed together for any given amount of fabric

Some characteristics that are used to identify fibers are the thread counts and the weave pattern.

Plants, animals, and minerals

Its ability to refract light

The fibers are easily woven and dyed

Rope

They do not contain any natural fibers

Are affected by microscopic organisms

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

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

1. The presence of a cuticle 2. The medullary index of 0.33 or less

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.

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.

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

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