Chp. 10 Hair Analysis - PowerPoint PPT Presentation

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Chp. 10 Hair Analysis
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Chp. 10 Hair Analysis

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  1. Chp. 10 Hair Analysis

  2. PLEASE DO NOW • How many hairs does the average person have on his/her head? • All • Brown hair • Red hair • Blond hair • What information can a forensic scientist determine from a human hair?

  3. 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

  4. 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

  5. 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

  6. Hair Growth • Anagen Phase • Cells in dermal papilla undergo mitosis and grow up to form hair shaft • Bulb is described as flame shaped

  7. 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

  8. 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

  9. 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

  10. 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

  11. Cuticle

  12. Cuticle • Viewing cuticle scales • Mount hair between glass slides • Prepare a clear cast of the cuticular surface • Scanning electron microscope

  13. 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

  14. Cortex

  15. Cortex

  16. 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

  17. Medulla

  18. 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

  19. 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

  20. 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

  21. 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

  22. Species Origin • Cuticle • Human • Imbricate scales = scales are small, flattened and with little serration • Animal • Exhibit a wide range of cuticular patterns

  23. Species Origin - Cuticle Mink Hair – Spinous Scales Human Hair – Imbricate Scales Bat Hair – Coronal Scales

  24. 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

  25. Species Origin - Cortex Pigment Distribution in Human Hair Pigment Distribution in Animal Hair

  26. 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

  27. Species Origin - Medulla Uniserial and Multiserial Ladder Medulla in Rabbit Hairs Vacuolated Medulla in Dog Hair Lattice Medulla in Deer Hair

  28. Racial Origin

  29. Caucasian Hair

  30. Mongoloid (Asian) Hair

  31. Negroid (African American) Hair

  32. 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 treated Pubic: 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 tufted Vulvar: Secondary pubic hair; finer and shorter; may be abraded Chest: Pectoral; moderate to considerable diameter variation; long fine archlike tip; usually longer than pubic hair Beard: 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/day Axillary: 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 bleached Eyebrow: 1 cm long; 0.16 mm/day growth; curved; relatively coarse for length; smooth curve with punctuate tip and large medulla Eyelash: Ciliary; less than 1 cm long; short curved pointed hair Limb: Leg and arm hair; 3-6 mm long; fine tip; irregularly medullated; often indistinctly and slightly pigmented Ear: Tragi; pinnae; downy Buttocks: Anal hair; short blunted and abraded hair Nose: Similar to facial hair (beard)

  33. Pubic Hair Limb Hair Beard Hair

  34. Association of Human Hair • Characteristics used for hair comparison • Structure • Color • Cuticular Traits • Length • Acquired Characteristics

  35. Structure of Hair

  36. Color of Hair

  37. Cuticular Traits

  38. Acquired Characteristics

  39. Razor Cut Scissor Cut Split End Broken/Clippers

  40. 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

  41. 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

  42. 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

  43. 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

  44. 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

  45. 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

  46. Identification Comparison DNA Review of Hair Analysis Collect Reference Samples

  47. Questions?