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Hair Evidence

Hair Evidence. Standard Students will demonstrate the ability to collect, preserve, and identify evidence found at a crime scene. Objectives 1. Describe the cuticle, cortex, medulla, and root of hair. 2. Explain the distinction between animal and human hairs.

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Hair Evidence

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  1. Hair Evidence Standard Students will demonstrate the ability to collect, preserve, and identify evidence found at a crime scene. Objectives 1. Describe the cuticle, cortex, medulla, and root of hair. 2. Explain the distinction between animal and human hairs. 3. List hair features that are useful for the comparison of human hair. 4. Explain the proper collection of hair evidence.

  2. The Biology of Hair • An appendage of the skin that grows out of an organ known as the hair follicle. • Extends from its root or bulb embedded in the follicle, continues into a shaft, and terminates at a tip end.

  3. The Shaft of Hair • Composed of three layers: cuticle, cortex, and medulla.

  4. Cuticle of Hair • Outside covering of hair that resists chemical decomposition. • Formed by overlapping scales that point towards the tip end of the hair. • Scales are made from hardened/keratinized cells that come 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.

  5. Cuticle Patterns • The coronal, or crown-like scale pattern, is found in hairs of very fine diameter and resemble a stack of paper cups. Coronal scales are commonly found in the hairs of small rodents and bats but rarely in human hairs. • Spinous or petal-like scales are triangular in shape and protrude from the hair shaft. They are found at the proximal region of mink hairs and on the fur hairs of seals, cats, and some other animals. They are never found in human hairs. • The imbricate or flattened-scale type consists of overlapping scales with narrow margins. They are commonly found in human hairs and many animal hairs

  6. Cortex of Hair • Found within the cuticle. • Made of spindle-shaped cortical cells aligned parallel to length of hair. • Within the cortex are pigment granules made by melanocytes that give 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.

  7. Your natural Hair color is determined by three factors 1. The type of natural color pigment melanin present in your hair's cortex. • Eumelanin (black pigment) • Phenomelanin (red/yellow pigment) 2. How many melanin granules exist 3. Whether those granules are close together or far apart

  8. How Melanin pigments determine your natural haircolor: • Black hair contains densely packed melanin granules full of eumelanin. • Brown hair has a loose pattern of eumelanin-filled granules or granules blended with eumelanin and phenomelanin, depending upon its cool or warm tones and its darkness or lightness. • Blonde hair contains few granules with minimal bits of eumelanin. In fact, the eumelanin is so sparse that the color of blonde hair is the color of the hair fiber itself. • Red hair has loosely packed granules containing phenomelanin.

  9. What causes gray hair? • As you age, your natural production of pigment slows down and your natural color loses its color strength. • This doesn't happen to every hair at the same time, so the contrast between the hair with no color and the hair that still has some color causes it to look gray. • So how gray your hair actually looks is determined by the percentage of strands with no color vs. the pigmented strands.

  10. Medulla of Hair • Collection of cells that look like a canal running through a hair. • Not all hairs have medullae • Can be classified as continuous ( most animals, human rare, Mongoloid race), fragmented (most animals, human) or absent (human).

  11. Medulla Shape • Humans and most animals cylindrical • Other animals  patterned (ex. Cat medulla looks like string of pearls, Deer medulla looks like round cells occupying the entire hair shaft)

  12. Examination of the Medulla

  13. Patterns in Animal Species Examination of Scale Pattern

  14. Medullary Index • By looking at the diameter of the medulla divided by the diameter of the hair shaft you can get the hairs’ medullary index. • Medullary Index Values •  Humans <1/3 •  Most other animals ≥1/2

  15. Comparison of Animal and Human Hair Humans Animals Medullary Index ≥1/2 Medulla is present for all animals Medulla is continuous for most animals Medulla is patterned for most animals Medullary Index <1/3 Medulla is absent for most humans Medulla is continuous for Mongoloid race Medulla is fragmented – only some animals and humans Medulla is cylindrical in shape (most animals)

  16. Human Hairs • Racial Determination • Body Area • Age and Sex? • Forcibly Removed?

  17. Racial Determination Usually kinky, containing dense, unevenly distributed pigments. Cross section is flat to oval in shape. Mongoloid Negroid Usually coarse containing pigment granules larger in size than Caucasians. Cross sections are round in shape. Cross section varieties. Usually straight or wavy with very fine to coarse pigments that are more evenly distributed . Cross section are oval to round in shape. Caucasoid

  18. Head Hairs • Long with moderate shaft diameter and diameter variation • Medulla absent to continuous and relatively narrow when compared to the structure of hairs from other body areas • Often with cut or split tips • Can show artificial treatment, solar bleaching, or mechanical damage • Soft texture, pliable

  19. Pubic Hairs Shaft diameter coarse with wide variations and buckling Medulla relatively broad and usually continuous when present Root frequently with tag Tip usually tapered, rounded, or abraded Stiff texture, wiry

  20. Limb Hairs Diameter fine with little variation Gross appearance of hair is arc-like in shape Medulla is discontinuous to trace with a granular appearance Tips usually tapered, often blunt and abraded, rounded scale ends due to wear Soft texture

  21. Facial Hairs (Beard/Mustache) • Diameter very coarse with irregular or triangular cross-sectional shape • Medulla very broad and continuous, may be doubled

  22. Chest Hairs • Shaft diameter moderate and variable • Tip often darker in color, long and fine, arc-like • Medulla may be granular • Stiff texture

  23. Axillary or Underarm Hairs • Resemble pubic hairs in general appearance, but less wiry • Medullary appearance similar to limb hairs • Diameter moderate and variable with less buckling than pubic hairs • Tips long and fine, frequently with bleached appearance

  24. Other Body Hairs • Eyebrow: Stubby, some diameter fluctuation, saber-like in appearance • Eyelash: Short, stubby with little shaft diameter fluctuation, saber-like in appearance • Trunk: A combination of features of limb and pubic hairs, a transitional hair

  25. Tip of the Shaft Burned Cut Razored Split

  26. Root of Hair • Provide the tools to produce hair and continue its growth • 3 Stages of Growth (different looking roots) • Anagen -initial phase may last up to 6 years, root is flame shaped • Catagen –transition phase (2-3 weeks), root is elongated • Telogen –phase where hair naturally falls out of the skin, root is club-shaped

  27. Hair Growth Cycle

  28. Forcibly Removed? Pulled Forcibly Removed Shed

  29. Brushed-out hairs all have this kind of root. A normal telogen hair with a hard 'club' end, seen under (left) a light microscope and (right) an electron microscope This is an anagen hair, one which was pulled out and not ready to be shed. An anagen hair that has been plucked out: notice the soft, sticky tail

  30. Collection of Hair Evidence

  31. Collection of Hair Evidence • Questioned and Reference hair must come from same area of the body; one cannot, for instance compare head hair to pubic hair. • The collection of 50 full length hairs from all areas of the scalp will normally ensure a representative sampling of head hair.

  32. Collection of Hair Evidence • A minimum collection of 24 full length pubic hairs should cover the range of characteristics present in this type of hair. • All collected hairs must be full-length so that the investigator can see if the color and morphological features vary throughout the length of the hair.

  33. Packaging 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

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