2IntroductionHuman hair is one of the most frequently found pieces of evidence at the scene of a violent crime. It can provide a link between the criminal and the crime.From hair one can determine:If the source is human or animalRace (sometimes)Origin of the location on the source’s bodyWhether the hair was forcibly removedIf the hair has been treated with chemicalsIf drugs have been ingested
5The Cuticle Clear outer covering with overlapping scales. Scales differ between species of animals.The three basic patterns are:CoronalSpinousImbricate
6The Cortex The cortex gives the hair its shape. It has two major characteristics:Melanin—pigment granules that give hair its colorCortical fusi—air spaces, usually found near the root but may be found throughout the hair shaft
7The Medulla Hair core Different types and patterns. Types: Intermittent or interruptedFragmentedContinuousStackedAbsent—not present
9Medullary Index Diameter of medulla Diameter of hair Human hair is usually 1/3Animal hair is usually 1/2.mouse
10Hair ShapeCan be straight, curly or kinky depending on the cross-section, which may be round, oval or crescent-shapedCrescent moon(Kinky)Round(Straight)Oval(Curly)
11Hair Growth Terminology Anagen—hair that is actively growing; lasting up to 5 yearsCatagen—hair is not growing; a resting phaseTelogen—hair that is dying and ready to fall out; lasting two to six monthsGrows about 0.5 mm per day or 1 centimeter per month; approximately 1/2 inch per month
12The Root Different if forcibly removed. Animal roots are generally spear shaped.Forcibly removedFallen out
13Hair Comparison Scale types Color Presence or absence of medulla Medullary typeMedullary patternMedullary indexColorLengthDiameterDistribution, shape and color intensity of pigment granulesDyed hair has color in cuticle and cortexBleaching removes pigment and gives a yellow tint
14DNA from Hair Roots contain nuclear DNA. Hair shaft contains mitochondrial DNA.It can be typed by comparing relatives if no DNA from the body is available.This process is more difficult and costly than using nuclear DNA.
15Collection of HairQuestioned hairs must be accompanied by an adequate number of control samples.from victimfrom possible suspectsfrom others who may have deposited hair at the sceneControl Sample50 full-length hairs from all areas of scalp24 full-length pubic hairs
16Hair Toxicology Advantages: Easy to collect and storeExternally availableProvides history of drug use and poisoning.Collections must be taken from different locations on the body to get an accurate timeline.
17Hair Toxicology Napoleon died in exile in 1821. By analyzing his hair, some investigators suggest he was poisoned by the deliberate administration of arsenic; others suggest that it was vapors from the dyes in the wallpaper that did him in.