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Hairs and Fibers

Hairs and Fibers. Morphology and Structure of Hair. Morphology (Structure) 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. The Shaft of Hair.

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Hairs and Fibers

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  1. Hairs and Fibers

  2. Morphology and Structure of Hair

  3. Morphology (Structure) 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.

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

  5. Morphology: Cuticle • Protective coating made of overlapping scales, produce a characteristic pattern • Scales always point toward tip of hair • Not useful in individualizing human hair • Can be used for species identification http://www.pg.com/science/haircare/hair_twh_35/hair_twh_35_02.jpg

  6. Preserving scale pattern • Since examination of internal structure of hair requires loss of scale pattern, a scale case is made. • Clear nail polish on microscope slide • Hair embedded and allowed to dry before removed.

  7. Differences between animal hairs & human hairs • There are three basic scale structures that make up the cuticle: • coronal (crown-like) • spinous (petal-like) • imbricate (flattened) Combinations and variations of these types are possible. http://www.fbi.gov/hq/lab/fsc/backissu/jan2004/research/2004_01_research01b.htm

  8. Differences between animal hairs & human hairs • 1. Coronal, or crown-like scale pattern: • hairs of very fine diameter • resemble a stack of paper cups • commonly found in the hairs of small rodents and bats, but rarely in human hairs http://www.fbi.gov/hq/lab/fsc/backissu/jan2004/research/2004_01_research01b.htm

  9. Differences : animal hairs & human hairs 2. Spinous or petal-like scales: • triangular in shape and protrude from the hair shaft • are found at the proximal region of mink hairs and on the fur hairs of seals, cats, and some other animals • never found in human hairs http://www.fbi.gov/hq/lab/fsc/backissu/jan2004/research/2004_01_research01b.htm

  10. Differences between animal hairs & human hairs 3. Imbricate or flattened scales: • consist of overlapping scales with narrow margins • commonly found in human hairs and many animal hairs

  11. Differences between animal hairs and human hairs • Human hairs are generally consistent in color; whereas animal hairs may exhibit radical color changes in a short distance, called banding. • The pigmentation of human hairs is evenly distributed, or slightly more dense toward the cuticle; whereas the pigmentation of animal hairs is more centrally distributed, although more dense toward the medulla.

  12. Morphology: Cortex • Made of spindle-shaped cells aligned in a regular array, parallel to the length of the hair • Embedded with pigment granules that give hair its color • The color, shape and distribution of the granules provide points for forensic comparison www.pg.com/science/haircare/hair_twh_59.htm

  13. 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. Number of melanin granules 3. Spacing of those granules (close together or far apart)

  14. How Melanin pigments determine your natural hair color: • Black hair: densely packed melanin granules, full of eumelanin • Brown hair: loose pattern of eumelanin-filled granules or granules blended with eumelanin and phenomelanin • Blonde hair: 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: loosely packed granules containing phenomelanin

  15. 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.

  16. Morphology: Medulla • Canal-like structure of cells that runs through the center of the cortex

  17. Medullary Index • Measure of the diameter of the medulla relative to the diameter of the hair shaft • Usually expressed as a fraction • Humans: medullary index < 1/3 • Animals: medullary index > 1/2

  18. Medullae of Different Species

  19. Medulla Shape UNISERIAL (rabbit) • Medulla shape is another characteristic that varies from species to species MULTISERIAL (rabbit) VACUOLATED (dog, fox, common) LATTICE (deer) AMORPHOUS (human, common) 20

  20. Medulla of Different Species

  21. Forensic Analysis of Medulla • Presence of medulla varies quite a bit: even hair to hair • Human head hairs generally have no medulla or may be fragmented ones; except Mongoloid (Asian) race whose medulla is usually continuous • Most animals have medulla that is continuous or interrupted • The shape of the medulla can help identify a species • Examples: • Most animals and humans: cylindrical • Cats: string of pearls • Deer: spherical occupying whole hair shaft

  22. Comparison of Animal and Human Hair Humans Animals (non-humans) Medullary Index ≥1/2 Medulla is present for all animals Medulla is continuous for most animals Medulla is patterned for most animals The pattern can tell the species! 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)

  23. Identification and Comparison of Hair • Morphological Characteristics do not allow individualization of a human hair to any single head or body • Hair when collected with an adequate number of standards/references can provide strongcircumstantial evidence • Scale structure, medullary index, and medullary shape are most often used for hair comparison

  24. Human Hairs(Testify) • Racial Determination • Body Area • Age and Sex? • Forcibly Removed?

  25. Can the racial origin of hair be determined? • Forensic terms: Caucasoid, African/West India, Mongoloid • Mongoloid has continuous medullae • Caucasian has even distribution of pigment in cortex • African/West India has unevenly distributed pigment. http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric1.htm

  26. Racial Determination Usually kinky, containing dense, unevenly distributed pigments. Cross section is flat to oval in shape. Mongoloid African 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

  27. 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

  28. 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

  29. 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

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

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

  32. 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

  33. 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

  34. Tip of the Shaft Burned Cut Razored Split

  35. 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

  36. Hair Growth Cycle

  37. Forcibly Removed? Pulled Forcibly Removed Shed

  38. 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

  39. Collection of Hair Evidence

  40. 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.

  41. 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.

  42. What does this mean…..? • To victims of a Sexual Assault? Do you think this would increase or decrease the likelihood that a person would file charges against their attacker?

  43. 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.

  44. 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

  45. Fibers…. • Fall into two main categories…. • 1. Natural non- synthetic • 2. Man- Made  synthetic

  46. Fibers: Natural---Non-synthetic • Derived entirely from animal or plant sources • Most prevalent plant fiber is cotton. • Its widespread use has made its evidential value almost meaningless • Cotton has a ribbon-like shape with twists at regular intervals • Animal sources include sheep (wool), goats (mohair, cashmere) and many other sources Cotton Wool http://www.swicofil.com/images/cotton_microscopic.jpg http://www.e4s.org.uk/textilesonline/content/6library/report1/images/microscope_2.gif

  47. Trace > Fibers > Natural jute Other Plant Fibers: Linen - stem fiber from flax plant Kapok - from seed hairs of kapok plant Other fibers - Manila, hemp, sisal, jute Cotton Hemp Linen sisal

  48. Trace > Fibers > Natural Mineral Fibers Asbestos - crystalline material • Used to be used for insulation • Fractures into thin rods that can get into your lungs; can kill you • Not used much anymore

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