Forensics Unit 2 Notes
Chapter 5 – Hair
I.
Form and Structure of Hair
a. Must understand form and structure or morphology of hair
b. Hair- made of mostly protein polymers- many identical repeating units (natural or synthetic)
c. Cuticle- tough, clear outside covering of hair shaft
d. Cortex- middle layer, gives strength and mass
i. Keratin-tough protein polymer made up of about 20 amino acids
e. Medulla- spongy interior, appears as a canal
i. Patterns vary between species
f. Cross sections- risky to assign racial characteristics to hair however…
i. Round- Asian or Native American
ii. Oval- European, Mexican and Middle Eastern
iii. Crescent moon- African
II.
Use in Forensics
a. Association- link between an unknown sample and a known sample
b. Questioned- sample of unknown origin
i. Hair found on jacket but do not know hose head it cam from
c. Exemplar- sample of known origin
i. hair was taken from so-and-so’s scalp (victim, suspect…)
d. A chemical indicator
i. Ingested chemicals are deposited in the cortex
e. Many drugs and their metabolites can be detected in just a few millimeters of hair
f. Metabolites- a specific product of a substance, formed by chemical processes in the body
g. Some analysis of hair may give a false positive b/c hair can absorb chemicals from your
surroundings
h. False positive- a test result that comes out positive when it should not
i. Ex: absorption of smoke from crack does not mean that crack was smoked