Forensics Fibers Vocabulary

What is the difference between a fabric and a fiber?

Fabric is made of fibers. Fibers are made of twisted elements that are either natural or artificial.

Fabric

In this context, a cloth material made up of fibers woven or bonded together in a distinctive manner

Fibers that come from a plant source.

Linen, cotton

Is silk synthetic or natural?

Natural

What is the most common type of synthetic fiber?

Nylon

List tests we did not do in the labs.

Refractive index, chromotagraphy, density, burn test, thermal decomp., chemical testing

Fibers

Usually made up of many filaments twisted or bonded together to form a thread or yarn

Who is the first person convicted on the basis of fiber evidence?

Wayne Williams

Can an investigator use the way a fabric accepts a specific dye to identify and compare samples?

Yes

Can a piece of fabric be individualized to a particular garment?

Yes for a piece of fabric, no for an individual fiber

Polypeptide

a biochemical polymer formed by linking amino acids; the longer chains are called proteins

Yarn

a continuous strand of fibers or filaments, either twisted or not

Blend

a fabric made up of two or more different types of fiber, usually as warp or weft

Becke Line

a halolike shadow appearing around an object immersed in a liquid of a different refractive index

Chromatography

a method of separating components of mixtures based on preferential adsorption partitioning of components in a gas, liquid, or solution. In paper chromatography, the cellulose of the paper acts as the absorbing medium. In thin-layer chromatography, the silica gel or alumina selectively adsorbs the components of the mixture.

Density

a physical property of matter. D= mass of object/ volume of object

Retention Factor

a ratio used to characterize and compare components of samples in liquid chromatography

Polyethers

a series of carbon atoms connected by oxygen atoms

Catalyst

a small amount of a substance that increases the rate of a reaction without being used up in the process

Helix

a spiral arrangement, like a corkscrew, of a long-chain molecule

Fibers that come from a mineral source.

asbestos, mineral wool

List properties that should be examined when comparing two fibers.

color, density, diameter, birefringence, fluorescence

Optical Brighteners

colorless dyes that cause blue light to be reflected, thereby making an object look whiter

What is the most common type of natural fiber?

cotton

List examples of natural fibers.

cotton, wool, linen, silk, cashmere, jute

Textiles

fabrics woven in a distinctive pattern (although bonded textiles, such as felt, lack a pattern)

The Amanda Davis case showed the importance of what?

fiber transfer

List examples of synthetic fibers.

nylon, polyester, acrylic, plastic, rayon, acetate, Dacron

Homopolymers

polymers made up of one type of repeating unit. each is made from one monomer only.

What is an electropherogram?

post of results from analysis done by eletrophoresis.

inorganic

refers to substances not composed primarily of hydrocarbons, that is carbon and hydrogen. Examples are asbestos and fiberglass.

Plain

simplest and most common weave. the warp and weft yarns pass under each other alternating.

Filaments

single strands of material, usually twisted with other filaments to make a thread or fiber

Plastics

substances that flow under heat and pressure and can, therefore, be molded into various shapes. All plastics are polymers, but not all polymers are plastics.

Fluorescence

the absorption of light as one wavelength (often in ultraviolet range) and its remission at a longer wavelength (often in the visible part of the spectrum)

Weft or Woof

the crosswise yarn or thread in a weave

Warp

the lengthwise yarn or thread in a weave

Keratin

the main protein in all human hair

What is optical microscopy?

the most important method of fiber identification that involves polarizing light and comparison microscopes.

Chromatogram

the record of chromatographic separation

Viscosity

the resistance of a fluid to flow. water has a low viscosity relative to syrup. heating generally lowers the viscosity of a liquid

Twill

the warp yarn is passed over one to three weft yarns before going under one. makes a diagonal weave pattern. design looks like stairs. example- denim jeans

Elute

to extract one material from another, usually by means of a solvent

What characteristics are indicative of synthetic fibers?

uniform shape of the cross section (can be different shapes), stronger and more chemically inert

Satin

yarn interacting is not uniform. creates long floats. interlacing weave passes four of more yars. satin is the most obvious example.

Can fiber evidence have probative value?

yes