Trace Evidence – Trace Evidence – hairhair

Chapter 5Chapter 5

Function of HairFunction of Hair

• All mammals have hairAll mammals have hair• Regulates body temperatureRegulates body temperature• Decrease frictionDecrease friction• Protect against sunlightProtect against sunlight• Sense organSense organ

Form and structureForm and structure

• Hair follicles are formed when a Hair follicles are formed when a fetus is 5 monthsfetus is 5 months

• Body has about 5 million hairsBody has about 5 million hairs• Blondes – 120,000 on headBlondes – 120,000 on head• Brunettes – 100,000Brunettes – 100,000• Redheads – 80,000Redheads – 80,000• We lose about 100 hairs a day.We lose about 100 hairs a day.

• Root is embedded in the follicle Root is embedded in the follicle where blood is supplied. where blood is supplied.

• Hair shaft grows through the Hair shaft grows through the epidermis. (cuticle, cortex, epidermis. (cuticle, cortex, medulla)medulla)

• Cuticle – made of overlapping Cuticle – made of overlapping scalesscales– Human scales (imbricate) are finer Human scales (imbricate) are finer

than animal scalesthan animal scales

– The scales point from the The scales point from the proximal (near head) to the distal proximal (near head) to the distal endend

• CortexCortex– Made of keratinMade of keratin– Contains pigment (melanin)Contains pigment (melanin)

• MedullaMedulla– May be dark or translucent May be dark or translucent

depending whether there is air, depending whether there is air, liquid, or pigment liquid, or pigment

– Can be continuous, interrupted, Can be continuous, interrupted, fragmented, solid, or nonefragmented, solid, or none

6 types of hair6 types of hair

• HeadHead• Eyebrows and eyelashesEyebrows and eyelashes• Beard and mustacheBeard and mustache• UnderarmUnderarm• Auxiliary or bodyAuxiliary or body• pubicpubic

Hair shapesHair shapes

• Straight, curly, kinky Straight, curly, kinky • Depends on the shape of the hair Depends on the shape of the hair

cross-sectioncross-section– Round: straight (Asians, Native Am.)Round: straight (Asians, Native Am.)– Oval: curly (Americans, Europeans, Oval: curly (Americans, Europeans,

Mexicans, Middle Eastern descent)Mexicans, Middle Eastern descent)– Crescent moon: kinky (African Crescent moon: kinky (African

American), dense pigmentationAmerican), dense pigmentation– Beard: coarse and triangularBeard: coarse and triangular

caucasiannegroid

mongoloid

Growth infoGrowth info

• Grows 1 cm per monthGrows 1 cm per month• New hair every 3-5 yearsNew hair every 3-5 years• 3 stages:3 stages:– Anagen: up to 5 yearsAnagen: up to 5 years– Catagen: intermediateCatagen: intermediate– Telogen: mature (follicle is ready to Telogen: mature (follicle is ready to

push out hair – 8-10% of follicles)push out hair – 8-10% of follicles)

• Mature hairs will have a bulb-like rootMature hairs will have a bulb-like root• Immature hair forcibly removed will Immature hair forcibly removed will

have follicular sheath presenthave follicular sheath present• Animal roots are typically spear-Animal roots are typically spear-

shapedshaped• Tip of hair will taper if uncut and not Tip of hair will taper if uncut and not

abusedabused• Tip is squared off, if recently cut (only Tip is squared off, if recently cut (only

2-3 weeks)2-3 weeks)

Racial differencesRacial differences

• European – straight, wavy, pigment European – straight, wavy, pigment granules evenly distributed, oval cross-granules evenly distributed, oval cross-section, color may be blond, brown, red, or section, color may be blond, brown, red, or blackblack

• Asian – straight, dense pigment granules, Asian – straight, dense pigment granules, round cross-section, coarse and straight, round cross-section, coarse and straight, thick cuticle, continuous medullathick cuticle, continuous medulla

• African – kinky, curly or coiled, dense and African – kinky, curly or coiled, dense and clumped pigment granules, flattened cross-clumped pigment granules, flattened cross-sectionsection

Animal vs . Human Animal vs . Human

AnimalAnimal• Pattern of pigmentation Pattern of pigmentation

varies widelyvaries widely• Pigment dense toward Pigment dense toward

medullamedulla• Color found in ovoid Color found in ovoid

bodies and colors bodies and colors change in banded change in banded patternpattern

• Medullary Index – 0.50 Medullary Index – 0.50 or moreor more

HumanHuman• Pigment dense toward Pigment dense toward

cuticlecuticle• One color along One color along

length of hairlength of hair• Medullary index 0.33 Medullary index 0.33

or lessor less

AnimalAnimal• Coronal cuticle – looks Coronal cuticle – looks

like a stack of crowns like a stack of crowns (rodents and bats)(rodents and bats)

• Spinous – look like Spinous – look like petals (cats, seals, petals (cats, seals, mink)mink)

HumanHuman• Imbricate – flattened Imbricate – flattened

and narrowand narrow

MicroscopyMicroscopy

• Phase contrast microscopy – can Phase contrast microscopy – can help see very fine detailshelp see very fine details

• Fluorescence – will show whether Fluorescence – will show whether a dye is presenta dye is present

• Electron microscopy – magnifies Electron microscopy – magnifies 50,000 times or more50,000 times or more

Testing for Testing for substancessubstances

• Dissolving in an organic solvent which Dissolving in an organic solvent which breaks down the keratin and releases the breaks down the keratin and releases the chemicals inside the hairchemicals inside the hair

• Time since exposure can be measured by Time since exposure can be measured by using the amount hair grows in one using the amount hair grows in one month(1.3cm) Ex: if toxin is found 9cm month(1.3cm) Ex: if toxin is found 9cm down from root, when did the person take in down from root, when did the person take in the toxin?the toxin?

• Neutron activation analysis – can identify up Neutron activation analysis – can identify up to 14 different elements in 2cm of hair. The to 14 different elements in 2cm of hair. The chance for two people to have 9 elements chance for two people to have 9 elements alike is one in a million. alike is one in a million.

What can hair tell What can hair tell us?us?

• Animal or humanAnimal or human• RaceRace• Body locationBody location• Chemical treatmentChemical treatment• ColorColor• How hair was removedHow hair was removed

• DrugsDrugs• Metal poisoningMetal poisoning• Things from the environment Things from the environment

stick to oilsstick to oils• Can cause false positivesCan cause false positives• DNADNA