forensic science - hair analysis

comparison microscope

compound microscope that allows side by side comparison of samples, such as hair

cortex

region of hair located outside the medulla that contains granules of pigment

cuticle

tough outer covering of hair thats composed of overlapping scales

gas chromatography

method of seperating chemicals to establish their quantities

hair follicle

activley growing part of hair that contains DNA and living cells

hair shaft

part if hair follicle that contains mitochondrial DNA

Isotope

different forms of an element that differ in atomic mass and number of nuetrons

isotope signiture

aka isotope fingerprint, is a ratio of different isotopes found in an individuals

isotope ratio mass spectometry (IRMS)

technology that allows examiners to analyze ratios of isotopes of oxygen, hydrogen, carbon, nitrogen, and sulfur

keratin

type of tiberous protein that makes up majority of the cortex of a hair

medulla

central core of a hair

melanin granules

particles of pigment found in the cortex of a hair

mitochondrial DNA

genetic material in mitochondrial of cyptoplasm of a cell, only inherited from mom

nuclear DNA

genetic material in a nucleus of cell

nuetron activation analysis (NAA)

a process that relies on determining concdentrations of elements in materials by creating radioactive decay paths that can be identified and used to date

Explain why hair is a valuable source of evidence (characteristics)

adheres to many surfeces, easily transfers to a victim or crime scene, tough outer coating, provides class evidence

Explain why hair is a valuable source of evidence (source of DNA)

hair with follice/root contains nuclear DNA and provides individual evidence, hair without follicle contains mitochondrial DNA and reveals family relationships

Explain why hair is a valuable source of evidence (chemical testing)

gas chromatography, isotope ratio analysis (cannot determine when hair was left)

1800s

regognize importance of hair as trace evidence

1900s

study published in france, 1st use of comparison microscope

2000s

(OSAC, NIST, POJ), greater training for technicians, equipment certification, no convictions soley on hair analysis, innocence project

functions of hair

regulates body temp, decreases friction, protects skin from sunlight

follicle

papilla (area containing capillaries), contains DNA and blood vessels

Hair Shaft

nongrowing part of hair, contains mitochonfrial DNA

4

cuticle

5

cortex

6

medulla

anagen stage

1,000 days (80-90% of hair)

catagen stage

hair stops growing, follicle recedes due to blood supply(2% of hair)

telogen stage

dormant hairs that are lost (10-18% of hair)

types of hair

varies in shape, length, diameter, texture, and color

kinds of hair

head, eyebrows, eyelashes, beard, mustach, underarm, pubic, body

treated hair

bleaching, dyeing, determinign PMI

ethnic differences

key physical characters (european, asian, african)

differences between nonhuman and human hair

human hair is usually 1 color along entire lenth, ratio of diameter of medulla to diameter of entire hair is medullary index, human scales are flattened and narrow

how to properly collect attached hair

leave hair intact, diagram and note exact location, photograph hair, package clothing w hair (if dry)

how to properly collect unattached hair

photograph in situ, use clean forceps, place hair in small box or vial, once in lab hair may be removed

microscopic analysis

low power compound, phase contrast microscopy, flouresence

macroscpoic analysis

seen w naked eye

chemical analysis

anything ingested/ ansorbed through skin, hair does not readily decompose, can establish a timeline

DNA analysis

hair containing follicle or root, individual evidence can be obtained

nuetron activation analysis (NAA)

creates radioactive decay paths

protein analysis

provides individual analysis