Human Hair Analysis Hair and Fiber 1. Hair Analysis Encountered in a wide variety of crimes...

Human Hair AnalysisHuman Hair AnalysisHair and Fiber 1Hair and Fiber 1

Hair AnalysisHair Analysis

Encountered in a wide variety of Encountered in a wide variety of crimescrimes Especially useful in rape casesEspecially useful in rape cases Also useful in illegal drug usage cases Also useful in illegal drug usage cases

(toxicology)(toxicology) Many attempts have been made to Many attempts have been made to

positively identify a suspect but all positively identify a suspect but all have failedhave failed Hair is usually class characteristic onlyHair is usually class characteristic only

Typically need more than oneTypically need more than one

Vital PropertiesVital Properties

Species identificationSpecies identification Color/PigmentColor/Pigment LengthLength DiameterDiameter Internal characteristicsInternal characteristics Dye/BleachingDye/Bleaching

Hair as EvidenceHair as Evidence

Hair evidence is evaluated by Hair evidence is evaluated by physical microscopy or chemical physical microscopy or chemical analysisanalysis

ToxicologyToxicology Hair acts like a time capsuleHair acts like a time capsule Base of hair shows most recent useBase of hair shows most recent use Protein structure “freezes” evidence of Protein structure “freezes” evidence of

drugs, heavy metals, etc. in hairdrugs, heavy metals, etc. in hair Typical human head hair growth is 1 cm Typical human head hair growth is 1 cm

per monthper month Rape/HomicideRape/Homicide

Source of DNA in follicular tissueSource of DNA in follicular tissue

Hair as EvidenceHair as Evidence

Species identificationSpecies identification Most species of mammals are Most species of mammals are

distinctly different from each other distinctly different from each other under a microscopeunder a microscope

Human ethnicityHuman ethnicity Can usually identify ethnicity in Can usually identify ethnicity in

humanshumans

Human EthnicityHuman Ethnicity CaucasoidCaucasoid

Usually straight or wavyUsually straight or wavy Evenly distributed, usually fine pigmentationEvenly distributed, usually fine pigmentation Oval to round cross sectionOval to round cross section Fragmented/absent medullaFragmented/absent medulla

MongoloidMongoloid Usually straightUsually straight Usually even, dense pigmentationUsually even, dense pigmentation Continuous medulla (defining characteristic)Continuous medulla (defining characteristic)

NegroidNegroid KinkyKinky Dense, unevenly distributed pigmentDense, unevenly distributed pigment Flat to oval cross sectionFlat to oval cross section Fragmented/absent medullaFragmented/absent medulla ““Buckling” often seenBuckling” often seen

Typical human hair cross sections

Hair Evidence MythsHair Evidence Myths

AgeAge Age can not be determined with any amount Age can not be determined with any amount

of certaintyof certainty Only infants seem to have distinct Only infants seem to have distinct

characteristicscharacteristics Usually very fineUsually very fine

GenderGender Gender can not be determined without Gender can not be determined without

follicle and DNA analysisfollicle and DNA analysis Male/Female structure identicalMale/Female structure identical Differences mainly genetic in natureDifferences mainly genetic in nature

Hair Evidence MythsHair Evidence Myths

DNA extractionDNA extraction Can be extracted from follicular tissue Can be extracted from follicular tissue

or root (in some cases)or root (in some cases) Cut hair without the root usually does Cut hair without the root usually does

not contain enough DNA to typenot contain enough DNA to type If forcefully removed, follicle tissue w/ If forcefully removed, follicle tissue w/

DNA likely attached to rootDNA likely attached to root Hair that falls out naturally does not Hair that falls out naturally does not

contain adhering tissuecontain adhering tissue

Body Hair TypesBody Hair Types

Forensically valuable hairForensically valuable hair Scalp hairScalp hair

Little diameter differencesLittle diameter differencesUniform pigmentUniform pigmentExposure to environmental conditions Exposure to environmental conditions

make immediate processing vitalmake immediate processing vital Pubic hairPubic hair

Vary widely in diameterVary widely in diameterUsually curlyUsually curlyShort lengthShort lengthLess exposure to elements allows for Less exposure to elements allows for

collection long after crimecollection long after crime

Body Hair TypesBody Hair Types Lesser forensic valueLesser forensic value

Most other body hairs are too variable in Most other body hairs are too variable in appearance to be valuable for forensicsappearance to be valuable for forensics

Characteristics are in no way linked to patterns Characteristics are in no way linked to patterns found on scalp hairfound on scalp hair

Can be used to determine a suspect’s presence Can be used to determine a suspect’s presence at scene but not often usedat scene but not often used

Three typesThree typesLimb - arm, legLimb - arm, legFringe hair - neck, sideburns, upper leg, backFringe hair - neck, sideburns, upper leg, backAxillary - eyebrows, nose, underarmAxillary - eyebrows, nose, underarm

Hair StructureHair Structure

Structural componentsStructural components EpidermisEpidermis

Outermost layer of skinOutermost layer of skin Pitted with hair folliclesPitted with hair follicles

RootRoot Portion of hair below skinPortion of hair below skin

FollicleFollicle Only segment of hair that Only segment of hair that

is livingis living Source cells from which Source cells from which

hair growshair grows Below skin in the bulbBelow skin in the bulb


Structural componentsStructural components Arrector (Erector) MuscleArrector (Erector) Muscle

Can cause hair to stand Can cause hair to stand on endon end

Also source of Also source of “goosebumps”“goosebumps”

Many animals have Many animals have control over these control over these musclesmuscles


Structural componentsStructural components Hair shaftHair shaft

Composed of protein Composed of protein keratinkeratinStructurally the same Structurally the same

as fingernailsas fingernailsThree layersThree layers

Cuticle, Cortex, Cuticle, Cortex, MedullaMedulla

Hair StructureHair Structure Structural componentsStructural components

CuticleCuticleProvides support for hairProvides support for hairNon-livingNon-livingConsists of overlapping Consists of overlapping

external scales different external scales different than most other than most other mammalsmammals

Scales very resistant to Scales very resistant to decompositiondecompositionMakes for perfect Makes for perfect

physical evidencephysical evidence


CortexCortex Inner layer of hairInner layer of hairContain pigment Contain pigment

granulesgranulesMelanin proteinMelanin protein

Distribution of pigment Distribution of pigment helps to determine helps to determine particular individualsparticular individuals


MedullaMedullaA “tube” of cells that run A “tube” of cells that run

up the center of the up the center of the cortexcortex

Width of medulla is Width of medulla is vitally important in vitally important in identifying speciesidentifying species

Ratio of hair width to Ratio of hair width to medulla width is called medulla width is called medullary indexmedullary index


MedullaMedulla Humans have less than 1/3 Humans have less than 1/3

medulla, most other medulla, most other animals at least ½animals at least ½

Comparison of human hair

(left), deer hair (top) and dog hair (right)


MedullaMedullaNot always present in Not always present in

certain ethnicitiescertain ethnicitiesOne person can have One person can have

multiple medulla multiple medulla structuresstructures

ContinuousContinuous InterruptedInterruptedFragmentedFragmented

Human Medulla TypesHuman Medulla Types

Typical human medulla types. From left to right: Continuous, Interrupted, Fragmented.


Artist’s conception and electron microscope images of a human hair with cuticle, cortex and (to a lesser extent) medulla

Hair GrowthHair Growth Growth cycle has three distinct phasesGrowth cycle has three distinct phases

Hair can stay on head for approx. 6 yearsHair can stay on head for approx. 6 years If forcefully pulled out and in one of first two If forcefully pulled out and in one of first two

phases, follicle tissue will likely be found phases, follicle tissue will likely be found with the hair folliclewith the hair follicle

(right) Diagram showing the

three phases of hair growth

Hair GrowthHair Growth AnagenAnagen

Up to six yearsUp to six years Root attached to follicleRoot attached to follicle Root will have a Root will have a

“flame” shape“flame” shape If pulled out, will usu. If pulled out, will usu.

have follicular tissue have follicular tissue and show evidence of and show evidence of stretching/forcestretching/force

Growth originates at Growth originates at base of hair and base of hair and grows upgrows up

80-90% of all hair will 80-90% of all hair will be in this phasebe in this phase

(Above)Electron microscope image showing new anagen follicles erupting from the epidermis. (Below) A typical

anagen follicle with attached tissue.

Hair GrowthHair Growth

CatagenCatagen Two to three weeksTwo to three weeks Growth slowerGrowth slower Root shrinks and is pushed out of Root shrinks and is pushed out of

folliclefollicle Usu. has a shrunken appearanceUsu. has a shrunken appearance 2% of all hair2% of all hair Transition phaseTransition phase

Hair GrowthHair Growth

TelogenTelogen Two to six monthsTwo to six months No growthNo growth Root has a club Root has a club

shape with no tissueshape with no tissue Is shed naturallyIs shed naturally 10-18% of all hair10-18% of all hair

A typical telogen hair follicle. Note the absence of

follicular tissue.

Hair MicroscopyHair Microscopy

Damaged cuticle showing loose scales.

Typical wear and tear with dislodged scales and

other debris on hair follicle.


Severely damaged hair that may be the result of

braiding or forceful removal.

A “split end” on a hair follicle. Also note evidence of cutting

by sharp scissors. Electric clippers usually leave much

more ragged marks.


A twisted/stretched root…clear indicator of forceful removal.

Tight, twisted appearance and scorch marks of hair exposed

to high heat.

The Atlanta Child MurdersThe Atlanta Child Murders 1979-1981, 29 black males were murdered 1979-1981, 29 black males were murdered

(ages 7-16 except for last 7 who were 17-27)(ages 7-16 except for last 7 who were 17-27) Strangled, beaten, asphyxiatedStrangled, beaten, asphyxiated

Only common evidence were fibers and Only common evidence were fibers and presence of dog hairpresence of dog hair

Two artificial fibers ID’edTwo artificial fibers ID’ed After info. leaked to press, M.O. changed and bodies After info. leaked to press, M.O. changed and bodies

were dumped in riverwere dumped in river PD staked out Chatahoochee RiverPD staked out Chatahoochee River

PD heard a loud splash and stopped a suspect (Wayne PD heard a loud splash and stopped a suspect (Wayne Williams)Williams)

Claimed it was garbageClaimed it was garbage Suspect released but body later found nearby Suspect released but body later found nearby

w/ single carpet fiber in hairw/ single carpet fiber in hair

The Atlanta Child MurdersThe Atlanta Child Murders

Warrant obtained for Williams’ house and Warrant obtained for Williams’ house and found matching carpet and dog hair/fibersfound matching carpet and dog hair/fibers Expert assistance obtained from DuPont Expert assistance obtained from DuPont

corporationcorporation Exhaustive use of statistical likelihood of Exhaustive use of statistical likelihood of

particular carpet being found in a single particular carpet being found in a single Atlanta home 1:7792Atlanta home 1:7792

Additional fiber matches w/ victims’ found Additional fiber matches w/ victims’ found from Williams’ carfrom Williams’ car Chevrolet assisted in this part of investigationChevrolet assisted in this part of investigation Statistical possibility 1:3828Statistical possibility 1:3828

The Atlanta Child MurdersThe Atlanta Child Murders

Combined, 1:30 million Combined, 1:30 million chance of both matches chance of both matches being achievedbeing achieved In total, 29 fiber type In total, 29 fiber type

matches found between matches found between Williams’ possessions and Williams’ possessions and victimsvictims

Found guilty after 12 Found guilty after 12 hours of deliberationhours of deliberation Serving 2 life sentencesServing 2 life sentences Still maintains innocence Still maintains innocence

and has attempted and has attempted retrialsretrials

Wayne Williams at his arraignment in February 1982.

Human Hair Analysis Hair and Fiber 1. Hair Analysis Encountered in a wide variety of crimes...

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