Chapter 3 THE STUDY OF HAIRSept. 3, 2013

TrichologyThe scientific study of the structure, function, and diseases of human hair. Very valuable in Forensic Science

More resistant to decayRemains intact much longer

Class EvidenceMaterial that connects an individual or thing to a certain group.Cannot be used to identify a specific individual

Can identify a group or class that share similar hair type.

Secondary TransferPet hair

Analyzing Hair Physical Characteristics: Broad racial backgroundChemical Characteristics: Drug use and other toxins, heavy metals, nutritional deficiencies. Follicle present, potential to recover DNA

Individual Evidence A kind of evidence that identifies a particular person or thing

DNA Fingerprint

Trace Evidence: small but measureable amounts of physical or biological material found at a crime scene.

Comparison MicroscopeA compound microscope that allows the side-by-side comparison of samples, such as hair or fibers

Today! Neutron activation analysis and DNA fingerprinting and is considered a standard tool in trace evidence analysis.

Function of HairAll mammals have hair.Regulate body temperatureDecrease frictionProtect against sunlightSense OrganVery dense Hair=Fur

HairTemperature Regulation

Hair and muscles work together to regulate body temp.Muscles pull hair upright, creating pockets that trap airMuscles relax and hair flattens against the body, releasing trapped air

Humans are born with about 5 million hair follicles, only 2% of which are on the head. As humans age, hair density decreases

Structure of HairFollicle

The actively growing root or base of a hair containing DNA and living cells

PapillaNetwork of blood vessels that supply nutrients to feed the hair and help it grow.

Sebaceous gland (bulb)Secretes oil to help the hair conditionedErector muscle causes the hair to stand up

Structure of the Hair Shaft

Composed of the protein Keratin;

a type of fibrous protein that makes up the majority of the cortex of a hair. Makes hair both strong and flexible

• Inner Medulla, Cortex, and Outer Cuticle• Pencil

Hair The Cuticle

Transparent tough outer layer of the hair composed of overlapping scales.

The CortexThe region of a hair located outside of the medulla containing granules of pigment (melanin) which gives the hair its color.

The MedullaThe center of the hair, can be hollow or filled with cells. Classify hair into 5 different groups depending on the appearance of the medulla.

Hair Classification See Figure 3-6 on page 53

Continuous: one unbroken line of colorInterrupted: Pigmented line broken at regular intervalsFragmented: Pigmented line unevenly spacedSolid: Pigmented area filling both the medulla and the cortexNone: No separate pigmentation in the medulla

Types of HairHair can vary in so many ways! Cross section viewTexturesColorNot all hairs on a person’s head are exactly the same

Sample of 50 from headSample of 25 from pubic region

Hair in Different Regions of the Body

6 Types on Human BodyHead HairEyebrow and EyelashesBeard and MustacheUnderarm HairAuxiliary or Body HairPubic Hair

Body HairDistinguished by their Cross-sectional Shape

Head- circular or ellipticalEyebrow/eyelashes- also circular, but have tapered endsBeard- thick and triangularBody hair- oval or triangular (depending on shaved often or not)Pubic- oval or triangular

Life Cycle of Hair3 Stages of Development

Anagen Stage: lasts approximately 1,000 days. Period of active growth when the cells around the follicle are rapidly dividing and depositing materials with in the hair.

Catagen Stage: next stage as hair grows ad changes.

Telogen Stage: final stage, the follicle is dormant or resting and hairs are easily lost.

HairRacial Differences (page 55)Animal Hair and Human Hair

(page 55)Hair in an investigationMicroscopy

Substances in HairDrug TestsTimeline1.3 cm per month (.44 mm per day)

9 cm = approximately 7 months

NAA (Neutron Activation Analysis)

14 different elements in a single 2cm long strand

DNA Follicular tag