Chapter 13: trace evidence (hair and fiber)

three phases of hair growth

antagen, catagen, telogen

antagen

3-7 years of active growth phase

catagen

1-2 weeks of transition phase

telogen

3-6 weeks of resting phase (decay)

coronal scale pattern

small rodents and bats

spinous scale pattern

petal like

cats, seals, other animals

NEVER in humans

imbricate scale pattern

overlapping scales

found in humans!

cortex

main body of hair shaft

color, shape, and distribution can provide comparison points

medulla

cellular column running through cortex

humans occupy 25% of diameter

animals occupy 50% of diameter

three types of medulla

continuous, interrupted, fragmented

root

follicular tag: used for mitochondrial DNA analysis (maternal details)

natural fibers

derived from plants or animals

example of natural fiber (animal)

wool

example of natural fiber (plant)

cotton

example of natural fiber (protein)

silk: contains multiple amino acids

comes from cocoon of larvae from silkworms

manufactured fibers

man-made fibers (better quality) made from natural raw materials

regenerated from cellulose

example of manufactured fiber

cellulose: polysaccharide (cellulose ester, rayon, regenerated protein, rubber)

synthetic fibers

made from synthetic chemicals (man-made)

example of synthetic fiber (first)

nylon-6,6

changing amount of carbon chain gives different types of nylons

example of synthetic fiber (alcohol functional groups)

polyester

microscopic analysis of fibers

cross sections are extremely miniscule

shapes change depending on type of fiber

flame test analysis of fibers

results in different observations such as: burn rate (fast/slow), smoke/odor, and melting bead (residue)

melting bead result

leaves hard, dark, and round bead