Forensic Notes (Fiber Evidence)

Collection of Fiber Evidence3

Removed fibers should be folded into a small sheet of paper and stored in a paper bag

Keratin can be found on what other parts of your body

Skin

Medulla

The central canal running through most hairs.

What part of the hair strand is required to individualize it to a specific source?

The follicle cell

Unusual yellow and green carpet fibers

The piece of evidence used to implicate Wayne Williams in the murders

Plain Weave

The simplest and most common weave pattern The warp and weft yarns pass under each other alternately Design resembles a checkerboard

cuticle, cortex, medulla

The three main layers of the hair shaft are the:

What made the evidence used to convict Wayne Williams so unusual?

The yellow and green carpet fibers were not common in houses throughout Atlanta.

Fill in the blank

A fiber can be spun into a spinneret to make a ?

What can be determined by examining an unknown hair sample's length, shape, size, and color?

A person's DNA

anagen phase

Also known as growth phase; phase during which new hair is produced.

Fiber

Are considered class Evidence Have Probative Value Are common trace evidence at a crime scene Can be characterized based on comparison of both physical and chemical properties

Collection of Fiber Evidence1

Bag clothing items individually in paper bags. Make sure that different items are not placed on the same surface before being bagged

Microscopic Observation (Testing for Identification)

Color--compositional differences in the dyes Fibers surface--delustering particles that may be added by manufacturers

What are examples of natural fibers?

Cotton, silk, wool

What are not the recommended methods for the collection of hair evidence

Cutting the hair or ?

What was used as evidence in the Wayne Williams murder case?

Fiber evidence

Fabric is made of

Fibers

What protein is your hair primarily made up of?

Keratin

Collection of Fiber Evidence2

Make tape lifts of exposed skin areas of bodies and any inanimate objects

Natural fibers are classified according to their origin

Vegetable or cellulose, Animal or protein, Mineral

What did the Wayne Williams do that indicated he was following news coverage of the killers?

Wayne stripped his victims naked and threw then into the Chatahochee River.

The scale pattern

Which feature of hair is MOST important in making a species identification?

Blend

a fabric made up of two or more different types of fiber.

Natural

animal, vegetable, or inorganic

Fourier Transform infrared analysis (FTIR)

based on selective absorption of wavelengths of light

When using a microscope, how do you determine the power of the magnification?

Multiply the power of the ocular lens by the power of the objective

The follicular tag on a loose hair strand is what?

Nuclear DNA

What can a synthetic fiber made up of?

Nylon, polyester, acrylic, and spandex

The pigment granules that provide a red or blonde hair strand are called what?

Pheomelanin

Cortex

Pigment granules that impart hair with color are found in this

The Eumelanin

Produces brown to black pigments in the hair

Thermal decomposition

gently heating to break down the fiber to the basic monomers

Medullae may be classified as being:

interrupted or absent, continuous, fragmented

Density (Testing for Identification)

mass of object divided by the volume of an object

Pyrolysis gas chromatography

mass spectrometry (PGC-MS)- burns a sample under controlled conditions, separates and analyzes each combustion product

Refractive Index (Testing for Identification)

measuring the bending of light as it passes from air into a solid or liquid

Nylon (Synthetic Fibers)

most durable of man-made fibers; extremely light weight

Polyester (Synthetic Fibers)

most widely used man-made fiber

Types of fibers:

natural and artificial

Burning (Testing for Identification)

observation of how a fiber burns, the odor, color of flame, smoke and the appearance of the residue

Types of Synthetic Fibers

rayon, nylon, acetate, acrylic, spandex, polyester

Chemical tests (Testing for Identification)

solubility and decomposition

The Imbricate

type of scales commonly found in human hair

Fluorescence (Testing for Identification)

used for comparing fibers as well as spotting fibers for collection

Optical microscopy

uses polarizing light and comparison microscopes

You do what to see better detail?

you increase the magnification, so you can see better detail.

Type of Natural Fibers

Silk, Cotton, Wool, Mohair, Cashmere

Artificial

synthesized or created from altered natural sources

telogenic stage

the final phase of hair growth, which is easily removed from the scalp