Unit 2 Forensics (Hair and Fiber)

Keratin

A protein that composes hair, also found in toes and fingernails. Makes it strong and flexible

Cortex

2nd and thickest layer, also contains the most pigment. Also the most important part for determining from which person the hair came from.

Medulla

central core (may be absent)

Cuticle

Clear outer coating composed of overlapping scales

continuous medulla

one unbroken line of color

Interrupted medulla

pigmented line broken at regular intervals

fragmented medulla

pigmented line unevenly spaced

solid medulla

pigmented area filling both the medulla and the cortex

none medulla

no separate pigmentation in the medulla

Head hair

generally circular or elliptical in cross section

Eyebrows and Eyelashes

circular but often have tapered ends

Beard and mustache hair

tend to be thick and triangular

underarm hair

Can be oval or triangular

auxiliary or body hair

Can be oval or triangular

pubic hair

Can be oval or triangular

Anagen Stage

long, hair actively grows - the cells around the follicle rapidly divide and deposit materials in the hair.

Catagen stage

the hair grows and changes

Telogen stage

the follicle becomes dormant - hairs can be lost.

Imbricate

resembles a brick

coronal

shapes like a cone

spinous

looks like spines

.5 or greater

animal hair

.33 or less

person

Medullary index

medullary diameter/hair diameter

Macroscopic

investigation can indicate length, color, and curliness

Microscopic

investigation can indicate fine detail in hair structure

follicle

crucial for dna testing

Fibers

used to create a possible link between crime and suspect or to recreate a crime scene/ considered class evidence

Natural fibers

Come from plants (cotton) or animals (wool). Typically non-uniform and inconsistent in shape and structure

Manufactured fibers

Synthetics like rayon, acetate, and polyester, which are made from long chains of molecules called polymers. Typically uniform and consistent in shape and structure

Wool and Cashmere

Sheeps

Mohair

goats

Angora

rabbits

Silk

caterpillar cocoons

Plant fibers

absorb water and insoluble in water, very resistant to damage from harsh chemicals, dissolvable only by strong acids, becomes brittle over time.

Cotton

most common textile plant fiber

coir

from coconuts, is durable

Hemp, jute, and flex

from stems, grows in bundles

Manila and sisal

from leaves, deteriorates quickly

Artifical fibers

man-made fibers that originate from natural materials such as cotton or wood

Synthetic Fibers

Manufactured from chemicals, more than 50% of all fibers used in production of textile materials are synthetic or man made

Glass fiber

extremely tiny glass fibers

asbestos

group of six different materials made into fibers, fire resistant

Rayon

most common in this group imitates natural fibers, but stronger

Acetate

carpets

polyamide nylon

lightweight clothing

Polyester

polar fleece, wrinkle resistant, not easily broken down, added to natural fibers for strength

Nylon

easily broken down, similar to polyester

Acrylic

Inexpensive, balls easily, substitute for artificial wool or fur

Olefins

quick drying, resistent to wear

Chemical test

dissolves in strong acid (plant, silk, or manufactured) dissolves in strong base (wool)

Burn test

order of burning hair (animal), order of burning paper (plant), melts (manufactured)