Hair GrowthHair Growth Human hair diameter ranges from 25-125 µmHuman hair diameter ranges from 25-125 µm Coarse hairs grow slower & fall out less Coarse hairs grow slower & fall out less

frequently than fine hairsfrequently than fine hairs Head hair grows about 1 Head hair grows about 1 cmcm//monthmonth

Replaced about every 3-5 yrs with new hairReplaced about every 3-5 yrs with new hair Three stages of hair growth:Three stages of hair growth:

Anagen phaseAnagen phaseCatagen phaseCatagen phaseTelogen phaseTelogen phase

Stages of Hair GrowthStages of Hair Growth Anagen phaseAnagen phase

Period of active growthPeriod of active growthLasts up to 5 yearsLasts up to 5 yearsIncludes 80-90% of hair folliclesIncludes 80-90% of hair follicles

Catagen phaseCatagen phaseHair is not growing; resting phaseHair is not growing; resting phaseLasts about 3 weeksLasts about 3 weeks

Telogen phase Telogen phase Follicle is ready to push out the mature hairFollicle is ready to push out the mature hairLasts 2-6 weeksLasts 2-6 weeksIncludes 8-10% of hair folliclesIncludes 8-10% of hair follicles

Stages of Hair GrowthStages of Hair Growth

Hair RootHair Root

Important in classifying hairImportant in classifying hair Telogenic human hair have bulblike root shape Telogenic human hair have bulblike root shape

& lack pigment granules& lack pigment granules Anagenic human hair may have follicular tissue Anagenic human hair may have follicular tissue

still attached, look stretched, & have pigment still attached, look stretched, & have pigment granules presentgranules present

Animal hair roots are generally spade-shapedAnimal hair roots are generally spade-shaped

Hair RootHair Root

Human roots look different based on Human roots look different based on whether they have been forcibly removed or whether they have been forcibly removed or

they are telogen hairs that have fallen outthey are telogen hairs that have fallen out

Fallen out Forcibly removed

Mature HairMature Hair Should have bulb-shaped baseShould have bulb-shaped base Length of shaft varies Length of shaft varies

Some cut more frequently than othersSome cut more frequently than others Tip of shaft will taper to a pointTip of shaft will taper to a point

Recently cut hair is squared off at tipRecently cut hair is squared off at tip○ Becomes round after about 2-3 weeksBecomes round after about 2-3 weeks

Split ends are result of dryness Split ends are result of dryness due to abusedue to abuseLack of conditioningLack of conditioningHarsh chemicalsHarsh chemicalsHeat from flat irons, blow dryers, etcHeat from flat irons, blow dryers, etc

Hair at the Crime SceneHair at the Crime Scene Crime scene hair considered trace evidenceCrime scene hair considered trace evidence

Can be used to backup other circumstantial Can be used to backup other circumstantial evidenceevidence

Investigator must determine species firstInvestigator must determine species firstThe more hair samples an investigator examines, The more hair samples an investigator examines,

the betterthe better Hair can be valuable evidence becauseHair can be valuable evidence because

• It has wide range of class characteristicsIt has wide range of class characteristics• Is persistentIs persistent• Resists degradationResists degradation• Commonly found at crime scenesCommonly found at crime scenes

Hair ComparisonHair Comparison Investigator may associate unknown hair with Investigator may associate unknown hair with

an individual by comparing characteristics:an individual by comparing characteristics:• ColorColor• LengthLength• DiameterDiameter• Scale typesScale types• Presence/Absence of medullaPresence/Absence of medullao Medulla type, pattern & indexMedulla type, pattern & index

• Distribution, shape & color of pigment granulesDistribution, shape & color of pigment granules Dyed hair has color in cuticle & cortexDyed hair has color in cuticle & cortex

Bleaching removes pigment & gives yellow tintBleaching removes pigment & gives yellow tint

Hair ComparisonHair Comparison More characteristics that are similar, the More characteristics that are similar, the

greater degree of probabilitygreater degree of probability A single significant difference between A single significant difference between

unknown (questioned) & known (exemplar) unknown (questioned) & known (exemplar) hair strongly suggests separate sourceshair strongly suggests separate sourcesExample: hair found on victim is long, black, Example: hair found on victim is long, black,

round cross section with continuous medulla while round cross section with continuous medulla while suspect has long, black hair with round cross suspect has long, black hair with round cross section but no medullasection but no medulla

Hair ComparisonHair Comparison Hair evidence cannot be used to determine age or Hair evidence cannot be used to determine age or

sex of individualsex of individual

From hair, one can determine:From hair, one can determine:If the source is human or animalIf the source is human or animal

RaceRace

SometimesSometimes

Location on the source’s bodyLocation on the source’s body

Whether the hair was forcibly removedWhether the hair was forcibly removed

If the hair has been treated with chemicalsIf the hair has been treated with chemicals

If drugs have been ingestedIf drugs have been ingested

DNA from HairDNA from Hair If hair has been forcibly removed, some follicular If hair has been forcibly removed, some follicular

tissue containing DNA may be attachedtissue containing DNA may be attachedHair root contains nuclear DNAHair root contains nuclear DNA

Hair shaft may contain mitochondrial DNA Hair shaft may contain mitochondrial DNA Can be typed by comparing relatives if no DNA from Can be typed by comparing relatives if no DNA from

the body is availablethe body is availableProcess is more difficult & more Process is more difficult & more

costly than using nuclear DNA costly than using nuclear DNA

Collection of HairCollection of Hair

Questioned hairs must be accompanied by an Questioned hairs must be accompanied by an adequate number of control samplesadequate number of control samplesFrom victimFrom victimFrom possible suspectsFrom possible suspectsFrom others who may have deposited hair at the From others who may have deposited hair at the

scenescene Control sampleControl sample

50 full-length hairs from all areas of scalp50 full-length hairs from all areas of scalp24 full-length pubic hairs24 full-length pubic hairs

Hair ToxicologyHair Toxicology Advantages:Advantages:

Easy to collect & storeEasy to collect & storeIs externally availableIs externally availableCan provide information on the individual’s history of Can provide information on the individual’s history of

drug use or evidence of poisoningdrug use or evidence of poisoning Collections must be taken from different locations Collections must be taken from different locations

on the body to get accurate timeline on the body to get accurate timeline Backs up standard blood & urine testsBacks up standard blood & urine tests

Drugs typically gone from blood a few hours after useDrugs typically gone from blood a few hours after useSince hair grows about 1 Since hair grows about 1 cmcm//monthmonth, drug use can be traced , drug use can be traced

over longer period of timeover longer period of time Must be careful to rule out false positivesMust be careful to rule out false positives

Hair ToxicologyHair Toxicology

Napoleon died in exile in 1821Napoleon died in exile in 1821 By analyzing his hair, some By analyzing his hair, some

investigators suggest he was investigators suggest he was poisoned by the deliberate poisoned by the deliberate administration of arsenicadministration of arsenic

Others suggest that it was Others suggest that it was vapors from the dyes in the vapors from the dyes in the wallpaper that killed him wallpaper that killed him

Hair Follicle Drug Test

Hair Analysis Goes Hair Analysis Goes WrongWrong