Chp. 10 Hair Analysis

PLEASE DO NOW

1. How many hairs does the average person have on his/her head?a) All

b) Brown hair

c) Red hair

d) Blond hair

2. What information can a forensic scientist determine from a human hair?

Hair as Evidence

• Continually falls from the body– About 100 hairs fall out each day

• Not readily lost or displaced• Goes unnoticed by criminal• Not easily destroyed• Useful associative evidence since it

originates directly from the individual

Hair Structure

• Hair = epidermal appendage that grows out of the skin from an organ known as the follicle– Root = portion of hair that lies in follicle

• Bulb = enlarged base of root• Dermal papilla = connective tissue

surrounded by bulb– Shaft = portion of hair above skin’s surface

• Composed primarily of keratin• Feature unique to mammals

Hair Growth

• Average period of hair growth 1,000 days– Grows 1 cm per month

• 3 distinct growth phases– Anagen (80-90% of hairs)

• Follicle actively producing hair– Catagen (2% of hairs)

• Transitional period– Telogen (10-18% of hairs)

• Follicle dormant/resting

Hair Growth

• Anagen Phase– Cells in dermal

papilla undergo mitosis and grow up to form hair shaft

– Bulb is described as flame shaped

Hair Growth

• Catagen Phase– Cells in the shaft

continue to differentiate but no more pigmentation or color produced in hair towards root

– Bulb of the root shrinks and becomes surrounded by the club – a capsule of cells

Hair Growth

• Telogen Phase– Hair anchored in

follicle only by club– Germ cells below

club getting ready to form next hair

– Dermal papilla looks like a ball below germ cells waiting to be surrounded by next bulb

Hair Structure

• The shaft of the hair has 3 layers– Cuticle = thin translucent scale layer

surrounding shaft– Cortex = main body of hair shaft– Medulla = central canal-like structure

Cuticle

• Made up of overlapping, nonnucleated, pigment-free, keratinized cells that have formed scales– As many as 6 layers of scales per hair– Scales always point away from the root

• Outer and inner cuticle margins can be:– Cracked– Ragged– Serrated– Flattened

Cuticle

Cuticle

• Viewing cuticle scales– Mount hair between

glass slides– Prepare a clear cast

of the cuticular surface

– Scanning electron microscope

Cortex

• Composed of elongated keratinized filaments aligned together parallel to the length of the hair

• Contained within cells of cortex– Cortical fusi = delicate air spaces

• Vary in amount, size, shape and distribution• Appear dark with transmitted light and bright with

direct light– Hair pigment = solid structure that gives hair color

• Vary in size, shape, distribution and density• Appear dark and granular• Smaller than cortical fusi

– Ovoid bodies• Solid structures that are oval in shape• Larger than pigment granules

Cortex

Cortex

Medulla• Cellular column running

through the center of the cortex

• Function is to increase protective properties of hair by adding internal space

• Medulla structure on humans is amorphous

• Pattern can be absent, fragmental, interrupted, or continuous

• Appearance will vary from person to person and within hairs of the same individual

Medulla

Hair as Evidence• Class evidence• Have to compare evidence against reference

samples• To collect samples:

– Bright light aids in the visualization of questioned hairs at a crime scene

– Stored in paper packets or between sealed glass slides

– Wide transparent tape obtains difficult to see hairs from clothing and carpets

– Note location from where collected• To collect reference samples:

– Collected from both victim and suspect– About 50 samples collected for comparison– Should be combed and pulled to represent all

growth stages– Should be taken from each region of the area– Must represent any chemically treated areas of the

hair

Identification of Human Hair

• First step in the forensic investigation of human hair is to identify the hair in question in the following categories:– Species Origin– Racial Origin– Somatic Origin

• A direct comparison with a reference hair can only be made after the hair is classified in this way

Species Origin

• 3 Types of Animal Hairs– Vibrissa

• Tactile and sensitive whiskers• Largest and longest hairs on body usually

– Bristle/Guard• Coarse hairs that make up the protective

outer coat• Distinctive in appearance and morphology

between different animal families– Wool/Fur

• Fine short hairs that cover the body and make up the inner coat

• Provides insulation from wet and cold

Species Origin

• 4 Types of Human Hairs– Primordial

• Coarse and whisker like• Appear during 3rd month of gestation• Grow on upper lips, eyebrows, palms and soles of

fetus– Lanugo

• Fine, soft, unmedullated and unpigmented• Replace primordial hairs but shed after 6 months of

gestation– Vellus

• Fine, soft, unmedullated and short (2 cm)• Spread uniformly over body surface except for

palms, soles, lips, and nipples– Terminal

• Replace vellus hairs at specific sites and stages of life

• Scalp and eyebrows, pubic areas, face, chest, back, arms and legs

Species Origin

• Cuticle– Human

• Imbricate scales = scales are small, flattened and with little serration

– Animal• Exhibit a wide range of cuticular patterns

Species Origin - CuticleHuman Hair – Imbricate

ScalesMink Hair – Spinous Scales

Bat Hair – Coronal Scales

Species Origin

• Cortex– Human

• Untreated human hair is uniform in color• Pigmentation granules are evenly distributed

or slightly more dense toward cuticle – Animal

• Hairs exhibit rapid color changes along the shaft called banding

• Pigmentation granules are more dense toward the medulla

Pigment Distribution in Human Hair

Pigment Distribution in Animal Hair

Species Origin - Cortex

Species Origin

• Medulla– Human

• Rarely 1/3 width of hair shaft• Structure is amorphous• Pattern can be absent, fragmented,

interrupted, or continuous– Animal

• More than 1/2 width of hair shaft• Distinct medulla structure between

species

Uniserial and Multiserial Ladder Medulla in Rabbit Hairs

Vacuolated Medulla in Dog Hair

Lattice Medulla in Deer Hair

Species Origin - Medulla

Racial Origin

DiameterCross

SectionPigmentation Cuticle Undulation

Caucasian70-100

μmOval Even Medium Uncommon

Asian90-120

μm Round Dense Thick Never

African American

60-90 μm FlatDense and Clumped

- Prevalent

Caucasian Hair

Mongoloid (Asian) Hair

Negroid (African American) Hair

Somatic Origin

Scalp: Head hair, 100-1000mm long, 25-125 um diameter; 0.4 mm/day growth; small root; tapered tip; little diameter variation; various medullation; often with cut tips may be artificially treatedPubic: Pudendal; 10-60 mm long; coarse diameter and prominent diameter variation and buckling; broad medulla; follicular tags common; asymmetrical cross section twisted and may be straight, curved, or spirally tuftedVulvar: Secondary pubic hair; finer and shorter; may be abradedChest: Pectoral; moderate to considerable diameter variation; long fine archlike tip; usually longer than pubic hairBeard: Facial hair; very coarse; 50-300 mm long; large root, irregular structure; often triangular cross section; complex medullation; blunted or razor cut tip; grows 0.4 mm/dayAxillary: Arm pit; 10-50 mm long; grows 0.3 mm/day; coarse; blunt tip, abraded or frayed; usually straighter than pubic hair; many cortical fusi; sometimes yellowed and bleachedEyebrow: 1 cm long; 0.16 mm/day growth; curved; relatively coarse for length; smooth curve with punctuate tip and large medullaEyelash: Ciliary; less than 1 cm long; short curved pointed hairLimb: Leg and arm hair; 3-6 mm long; fine tip; irregularly medullated; often indistinctly and slightly pigmentedEar: Tragi; pinnae; downyButtocks: Anal hair; short blunted and abraded hairNose: Similar to facial hair (beard)

Pubic Hair Limb Hair

Beard Hair

Association of Human Hair

• Characteristics used for hair comparison– Structure– Color– Cuticular Traits– Length– Acquired Characteristics

Structure of Hair

Color of Hair

Cuticular Traits

Acquired Characteristics

Scissor Cut Razor Cut

Split End Broken/Clippers

Microscopy

• 3 types of microscope used:– Stereoscopic Microscope - gross observations of

the hairs• Study trace evidence on the hair’s surface, spatial

configuration, roots, and tips– Compound or Polarizing Microscope - allows for

higher magnification and resolution• Delineates hair’s finer structural characteristics

(pigment, scale, structure, cortical fusi, medulla)– Transmitted Light Comparison Microscope -

compare known and unknown hairs side-by-side

• Mounting choices– Dry mount– Temporary liquid mounting media– Permanent mounting media

Conclusions from Comparisons

• One of 3 conclusions can be reached:– The hairs matched in microscopic characteristics

indicating an association– The hairs were not alike and therefore did not

originate from the same individual– No conclusion can be drawn from the evidence

• Factors affecting degree of certainty associated with conclusion:– Number of unknown hairs found to be similar to

reference hairs– Number of microscopic features observed– The presence of unusual characteristics– Condition of specimens– Completeness of reference sample collection

Was Hair Forcefully Removed?• Look for follicular tag

– Tissue from the follicle attached to the root of the hair

– If a hair pulled from the body was securely attached to the follicle (anagen stage) a follicular tag will be present

• If there:– Yes hair was pulled out

• If absent:– Could have fallen out naturally– Could have been pulled out but cannot tell because

• If the hair was in the telogen phase, no tissue would be attached

• Some individuals lack follicular tissue on plucked anagen hairs

Naturally shed hairs dislodged through combing display

undamaged, club-shaped roots

A hair forcibly removed from the scalp will exhibit stretching and

damage to the root area

(PULLED)

Forcibly removed hairs may have tissue

attached called the follicular tag

Is Hair from a Dead Body?• Look for postmortem banding

– A dark band around the hair near the root where the skin surface meets the hair shaft

– Found on hairs pulled from decomposing skin

• If present:– May indicate that the body was moved after

death

Individualization of Human Hair

• DNA allows for the individualization of hair– Nuclear DNA

• Found in the follicular tag• Will identify hair with one individual

– Mitochondrial DNA• Found throughout cells of hair• Will identify hair to individuals of the same

maternal line

Quick Review

Human 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 animal Race (sometimes) Origin of the location on the source’s body Whether the hair was forcibly removed If the hair has been treated with chemicals If drugs have been ingested

Collect Reference Samples

Identification Comparison DNA

Review of Hair Analysis