Forensics: Hair and Fibers

The Principles & Practice of Medical Jurisprudence (1883) by Alfred Swaine Taylor and Thomas Stevenson

Contains chapter on hair analysis, drawings of hair under magnification, references English cases where hair was used

The Hair of Man and Animals (1910) by Victor Balthazard and Marcelle Lambert

Contains microscopic studies of hairs from many animals

Use of comparison microscope

Dr. Sydney Smith used to solve murder of 8-year-old girl in 1934

body hair

fine and short hair

head hair

hair that grows denser and longer

eyebrows

grows densely but shorter

pubic hair

coarse and curly hair

eyelashes

short and regular

mammals

All have hair (called fur if dense).

purpose of hair

regulate body temperature, decrease friction, protect against sunlight, act as a sense organ

hair follicle

where hair grows out of

parts of a hair

root, shaft, tip

parts of shaft

cuticle, cortex, medulla

root

bulb embedded in the hair follicle

growth phase

determines shape & size

Anagen

initial growth phase (6 years), root bulb has a flame-shaped appearance, follicular tag is translucent tissue with DNA, nourishment by blood supply enables hair growth

Catagen

transition phase (2-3 weeks), hair grows at decreasing rate, roots have elongated appearance, detaches from nourishing blood supply

Telogen

resting phase (2-6 months), hair naturally pushed out of follicle, root has club-shaped appearance, hair dies and falls our without nourishment

cuticle

scale structure covering exterior of hair

cuticle patterns used for species identification

coronal, spinous, imbricate

cortex

main body of hair shaft, gives hair its color

medulla

cellular column through center of hair

medullary index

diameter of medulla to diameter of shaft

human medullary index

less than 1/3

primary identification

color, length, diameter, medullary shape, pigment granules

secondary identification

growth, dye, fungal infections

50 full length hair

head hair reference sample

24 full length hair

pubic hair reference sample

natural fibers

derived from plant or animal sources

manufactured fibers

derived from natural or synthetic fibers

guard hairs

outer coat of the animal, protect inner hair and skin

sensory fur

tail and mane hairs

underfur or wool hairs

form the inner coat and provide insulation