Hair EvidenceHair Evidence

StandardStandard

Students will demonstrate the ability to Students will demonstrate the ability to collect, preserve, and identify evidence collect, preserve, and identify evidence

found at a crime scene.found at a crime scene.

ObjectivesObjectives1. Describe the cuticle, cortex, medulla, and root of 1. Describe the cuticle, cortex, medulla, and root of

hair.hair.

2. Explain the distinction between animal and 2. Explain the distinction between animal and human hairs. human hairs.

3. List hair features that are useful for the 3. List hair features that are useful for the comparison of human hair. comparison of human hair.

4. Explain the proper collection of hair evidence.4. Explain the proper collection of hair evidence.

The Biology of HairThe Biology of Hair

An appendage of An appendage of the skin that grows the skin that grows out of an organ out of an organ known as the hair known as the hair follicle.follicle.

Extends from its Extends from its root or bulb root or bulb embedded in the embedded in the follicle, continues follicle, continues into a shaft, and into a shaft, and terminates at a tip terminates at a tip end.end.

The Shaft of HairThe Shaft of Hair

Composed of Composed of three layers: three layers: cuticle, cortex, cuticle, cortex, and medulla.and medulla.

Cuticle of HairCuticle of Hair Outside covering of Outside covering of

hair that resists hair that resists chemical chemical decomposition.decomposition.

Formed by Formed by overlapping scales overlapping scales that point towards that point towards the tip end of the the tip end of the hair.hair.

Scales are made Scales are made from from hardened/keratinizehardened/keratinized cells that come d cells that come from the follicle. from the follicle.

Cuticle of a healthy hair. The scales lie flat, and are covered with oil, making the hair feel smooth and look glossy. The scales make the hair stiff, and protect the inside

A hair with a damaged cuticle, perhaps from brushing, coloring, or blow-drying. The hair looks dull, and scales flaking off may expose the inner layers, leading to further damage.

Cuticle PatternsCuticle Patterns The The coronalcoronal, or crown-like , or crown-like

scale pattern, is found in hairs of scale pattern, is found in hairs of very fine diameter and resemble very fine diameter and resemble a stack of paper cups. Coronal a stack of paper cups. Coronal scales are commonly found in the scales are commonly found in the hairs of small rodents and bats hairs of small rodents and bats but rarely in human hairs.but rarely in human hairs.

SpinousSpinous or petal-like scales or petal-like scales are triangular in shape and are triangular in shape and protrude from the hair shaft. protrude from the hair shaft. They are found at the proximal They are found at the proximal region of mink hairs and on the region of mink hairs and on the fur hairs of seals, cats, and some fur hairs of seals, cats, and some other animals. They are never other animals. They are never found in human hairs.found in human hairs.

The The imbricateimbricate or flattened- or flattened-scale type consists of scale type consists of overlapping scales with overlapping scales with narrow margins. They are narrow margins. They are commonly found in human commonly found in human hairs and many animal hairshairs and many animal hairs

Cortex of HairCortex of Hair

Found within the cuticle. Found within the cuticle. Made of spindle-shaped Made of spindle-shaped

cortical cells aligned cortical cells aligned parallel to length of hair.parallel to length of hair.

Within the cortex are Within the cortex are pigment granules made pigment granules made by melanocytes that give by melanocytes that give hair its color.hair its color.

Cortex of a damaged hair. A split end, caused when a hair shaft is pulled apart. Many split ends give hair a frizzy appearance, and cause tangles.

Your natural Hair color is Your natural Hair color is determined by three determined by three

factorsfactors

1. The type of natural color pigment 1. The type of natural color pigment melanin present in your hair's melanin present in your hair's cortex. cortex. Eumelanin (black pigment) Eumelanin (black pigment) Phenomelanin (red/yellow pigment) Phenomelanin (red/yellow pigment)

2. How many melanin granules exist 2. How many melanin granules exist

3. Whether those granules are close 3. Whether those granules are close together or far aparttogether or far apart

How Melanin pigments determine How Melanin pigments determine your natural haircolor: your natural haircolor:

Black hair contains densely packed melanin granules Black hair contains densely packed melanin granules full of eumelanin.full of eumelanin.

Brown hair has a loose pattern of eumelanin-filled Brown hair has a loose pattern of eumelanin-filled

granules or granules blended with eumelanin and granules or granules blended with eumelanin and phenomelanin, depending upon its cool or warm phenomelanin, depending upon its cool or warm tones and its darkness or lightness. tones and its darkness or lightness.

Blonde hair contains few granules with minimal bits Blonde hair contains few granules with minimal bits of eumelanin. In fact, the eumelanin is so sparse of eumelanin. In fact, the eumelanin is so sparse that the color of blonde hair is the color of the hair that the color of blonde hair is the color of the hair fiber itself. fiber itself.

Red hair has loosely packed granules containing Red hair has loosely packed granules containing phenomelanin. phenomelanin.

What causes gray hair?What causes gray hair? As you age, your natural production of As you age, your natural production of

pigment slows down and your natural pigment slows down and your natural color loses its color strength. color loses its color strength.

This doesn't happen to every hair at the This doesn't happen to every hair at the same time, so the contrast between the same time, so the contrast between the hair with no color and the hair that still hair with no color and the hair that still has some color causes it to look gray. has some color causes it to look gray.

So how gray your hair actually looks is So how gray your hair actually looks is determined by the percentage of determined by the percentage of strands with no color vs. the pigmented strands with no color vs. the pigmented strands. strands.

Medulla of HairMedulla of Hair

Collection of cells that look like a canal running Collection of cells that look like a canal running through a hair. through a hair.

Not all hairs have medullaeNot all hairs have medullae Can be classified as continuous ( most animals, Can be classified as continuous ( most animals,

human rare, Mongoloid race), fragmented (most human rare, Mongoloid race), fragmented (most animals, human) or absent (human).animals, human) or absent (human).

Medulla ShapeMedulla Shape

Humans and Humans and most animals most animals cylindricalcylindrical

Other animals Other animals patterned (ex. patterned (ex. Cat medulla looks Cat medulla looks like string of like string of pearls, Deer pearls, Deer medulla looks like medulla looks like round cells round cells occupying the occupying the entire hair shaft)entire hair shaft)

Examination of the MedullaExamination of the Medulla

Patterns in Animal SpeciesPatterns in Animal Species

Examination of Scale Pattern

Medullary IndexMedullary Index

By looking at the diameter of the By looking at the diameter of the medulla divided by the diameter of medulla divided by the diameter of the hair shaft you can get the hairs’ the hair shaft you can get the hairs’ medullary index.medullary index.

Medullary Index ValuesMedullary Index Values Humans <1/3 Humans <1/3 Most other animals Most other animals ≥1/2≥1/2

Comparison of Animal and Comparison of Animal and Human HairHuman Hair

Medullary Index ≥1/2

Medulla is present Medulla is present for all animalsfor all animals

Medulla is Medulla is continuous for most continuous for most animalsanimals

Medulla is patterned Medulla is patterned for most animalsfor most animals

Medullary Index <1/3

Medulla is absent Medulla is absent for most humansfor most humans

Medulla is Medulla is continuous for continuous for Mongoloid raceMongoloid race

Medulla is fragmented – only some animals and humans

Medulla is cylindrical in shape (most animals)

Human HairsHuman Hairs

Racial DeterminationRacial Determination Body AreaBody Area Age and Sex?Age and Sex? Forcibly Removed?Forcibly Removed?

Racial DeterminationRacial Determination

Negroid

Mongoloid

Caucasoid

Usually kinky, containing dense, unevenly distributed pigments.

Cross section is flat to oval in shape.

Usually straight or wavy with very fine to coarse pigments that are more evenly distributed .

Cross section are oval to round in shape.

Usually coarse containing pigment granules larger in size than Caucasians.

Cross sections are round in shape.

Cross section

varieties.

Head Hairs

Long with moderate shaft diameter and diameter variation Long with moderate shaft diameter and diameter variation

Medulla absent to continuous and relatively narrow when Medulla absent to continuous and relatively narrow when compared to the structure of hairs from other body areas compared to the structure of hairs from other body areas

Often with cut or split tips Often with cut or split tips

Can show artificial treatment, solar bleaching, or Can show artificial treatment, solar bleaching, or mechanical damage mechanical damage

Soft texture, pliable Soft texture, pliable

Pubic Hairs

Medulla relatively broad and usually continuous when present

Root frequently with tag

Tip usually tapered, rounded, or abraded

Stiff texture, wiry

Shaft diameter coarse with wide variations and buckling

Limb HairsLimb Hairs

Tips usually Tips usually tapered, often tapered, often blunt and blunt and abraded, abraded, rounded scale rounded scale ends due to ends due to wearwear

Diameter fine with little Diameter fine with little variation variation

Gross appearance of hair Gross appearance of hair is arc-like in shape is arc-like in shape

Medulla is Medulla is discontinuous to discontinuous to trace with a trace with a granular granular appearanceappearance

Soft textureSoft texture

Facial Hairs (Beard/Mustache)

Diameter very coarse with Diameter very coarse with irregular or triangular cross-irregular or triangular cross-sectional shape sectional shape

Medulla very broad and Medulla very broad and continuous, may be doubledcontinuous, may be doubled

Chest Hairs

Shaft diameter moderate and variable Shaft diameter moderate and variable

Tip often darker in color, long and fine, Tip often darker in color, long and fine, arc-like arc-like

Medulla may be granular Medulla may be granular

Stiff texture Stiff texture

Axillary or Underarm Axillary or Underarm HairsHairs

Resemble pubic hairs in general Resemble pubic hairs in general appearance, but less wiry appearance, but less wiry

Medullary appearance similar to limb hairs Medullary appearance similar to limb hairs

Diameter moderate and variable with less Diameter moderate and variable with less buckling than pubic hairs buckling than pubic hairs

Tips long and fine, frequently with bleached Tips long and fine, frequently with bleached appearanceappearance

Other Body Hairs

Eyebrow: Stubby, some diameter Eyebrow: Stubby, some diameter fluctuation, saber-like in fluctuation, saber-like in appearance appearance

Eyelash: Short, stubby with little Eyelash: Short, stubby with little shaft diameter fluctuation, saber-shaft diameter fluctuation, saber-like in appearance like in appearance

Trunk: A combination of features of limb Trunk: A combination of features of limb and pubic hairs, a transitional hair and pubic hairs, a transitional hair

Tip of the ShaftTip of the Shaft

Burned Cut Razored Split

Root of HairRoot of Hair Provide the tools to produce hair and Provide the tools to produce hair and

continue its growthcontinue its growth 3 Stages of Growth (different looking roots)3 Stages of Growth (different looking roots)

Anagen -initial phase may last up to 6 years, Anagen -initial phase may last up to 6 years, root is flame shapedroot is flame shaped

Catagen –transition phase (2-3 weeks), root is Catagen –transition phase (2-3 weeks), root is elongatedelongated

Telogen –phase where hair naturally falls out of Telogen –phase where hair naturally falls out of the skin, root is club-shapedthe skin, root is club-shaped

Hair Growth CycleHair Growth Cycle

Forcibly Removed?Forcibly Removed?

Pulled Forcibly Removed Shed

A normal telogen hair with a hard 'club' end, seen under (left) a light microscope and (right) an electron microscope

An anagen hair that has been plucked out: notice the soft, sticky tail

Brushed-out hairs all have this kind of root.

This is an anagen hair, one which was pulled out and not ready to be shed.

Collection of Hair EvidenceCollection of Hair Evidence

Collection of Hair EvidenceCollection of Hair Evidence Questioned and Reference hair Questioned and Reference hair

must come from same area of the must come from same area of the body; one cannot, for instance body; one cannot, for instance compare head hair to pubic hair.compare head hair to pubic hair.

The collection of 50 full length The collection of 50 full length hairs from all areas of the scalp hairs from all areas of the scalp will normally ensure a will normally ensure a representative sampling of head representative sampling of head hair.hair.

Collection of Hair Collection of Hair EvidenceEvidence

A minimum collection of 24 full length A minimum collection of 24 full length pubic hairs should cover the range of pubic hairs should cover the range of characteristics present in this type of characteristics present in this type of hair.hair.

All collected hairs must be full-length so All collected hairs must be full-length so that the investigator can see if the color that the investigator can see if the color and morphological features vary and morphological features vary throughout the length of the hair.throughout the length of the hair.

Packaging of Hair EvidencePackaging of Hair Evidence Recover all hair present. If possible, use fingers or tweezers to pick

up hair, place in paper bindles or coin envelopes which should then be folded and sealed in larger envelopes.

Label the outer sealed envelope. If hair is attached, such as in dry blood, or

caught in metal or a crack of glass, do not attempt to remove it but rather leave hair intact on the object.

If the object is small, mark it, wrap it, and seal it in an envelope.

If the object is large, wrap the area containing the hair in paper to prevent loss of hairs during shipment