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Fiber And Hair Evidence

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Fiber And Hair Evidence

  1. 1. Fiber and Hair Evidence
  2. 2. Fibers <ul><li>most often used as class evidence </li></ul><ul><li>can provide strong corroborating evidence to place perpetrator at crime scene </li></ul>
  3. 3. Fibers <ul><li>fiber </li></ul><ul><ul><li>many filaments twisted or bonded together to form thread or yarn </li></ul></ul><ul><li>filament </li></ul><ul><ul><li>single strand of material of indefinite length </li></ul></ul>
  4. 4. Fibers <ul><li>can be natural </li></ul><ul><ul><li>silk, wool, mohair, cashmere, angora, cotton, linen, jute, sisal, hemp, ramie, asbestos, fiberglass, rayon </li></ul></ul><ul><li>can be artificial or synthetic </li></ul><ul><ul><li>acrylic, aramid, nylon, olefin, spandex, polyester, modacrylic </li></ul></ul>
  5. 5. Fibers <ul><li>physical properties </li></ul><ul><ul><li>color </li></ul></ul><ul><ul><ul><li>chromatography of dyes </li></ul></ul></ul><ul><ul><ul><li>polarization with light </li></ul></ul></ul><ul><ul><li>blend and /or weave </li></ul></ul><ul><ul><li>diameter of fibers </li></ul></ul><ul><ul><li>cross sectional shape </li></ul></ul>
  6. 7. Fibers <ul><li>physical properties </li></ul><ul><ul><li># of filaments </li></ul></ul><ul><ul><li>density </li></ul></ul><ul><ul><li>refractive index </li></ul></ul><ul><ul><ul><li>refraction is the bending of light waves due to a change in the velocity </li></ul></ul></ul><ul><ul><li>fluorescence </li></ul></ul>
  7. 8. Fibers <ul><li>chemical properties </li></ul><ul><ul><li>burning tests (oxidation) analysis </li></ul></ul><ul><ul><ul><li>ash, behavior in and out of flame, odor </li></ul></ul></ul><ul><ul><li>thermal decomposition </li></ul></ul><ul><ul><ul><li>pH, residue and component chemicals </li></ul></ul></ul><ul><ul><li>chemical decomposition </li></ul></ul><ul><ul><ul><li>treatment with various strong acids, bases and solvents </li></ul></ul></ul>
  8. 9. Fibers <ul><li>many of these tests would be made between the unknown and </li></ul><ul><ul><li>reference samples taken at scene </li></ul></ul><ul><ul><li>reference samples taken from individuals involved at scene </li></ul></ul><ul><ul><li>exemplars – scientific standards accepted widely </li></ul></ul><ul><ul><ul><li>usually found in databases </li></ul></ul></ul>
  9. 10. Fibers <ul><li>many of these tests would be made between the unknown & </li></ul><ul><ul><li>reference samples taken at scene </li></ul></ul><ul><ul><li>reference samples taken from individuals involved at scene </li></ul></ul><ul><ul><li>exemplars – scientific standards accepted widely </li></ul></ul><ul><ul><ul><li>usually found in databases </li></ul></ul></ul>
  10. 11. Hair <ul><li>considered a type of fiber </li></ul><ul><li>not able to individualize unless DNA is present </li></ul><ul><li>w/o DNA, it can provide strong corroborative evidence for placing an individual at a crime scene </li></ul>
  11. 12. Hair <ul><li>morphology </li></ul><ul><ul><li>root </li></ul></ul><ul><ul><ul><li>in follicle </li></ul></ul></ul><ul><ul><li>shaft </li></ul></ul><ul><ul><ul><li>cuticle </li></ul></ul></ul><ul><ul><ul><li>cortex </li></ul></ul></ul><ul><ul><ul><li>medulla </li></ul></ul></ul><ul><ul><li>tip/end </li></ul></ul>
  12. 13. Hair <ul><li>morphology </li></ul><ul><ul><li>root </li></ul></ul><ul><ul><ul><li>in follicle </li></ul></ul></ul><ul><ul><li>shaft </li></ul></ul><ul><ul><ul><li>cuticle </li></ul></ul></ul><ul><ul><ul><li>cortex </li></ul></ul></ul><ul><ul><ul><li>medulla </li></ul></ul></ul><ul><ul><li>tip/end </li></ul></ul>
  13. 14. Hair <ul><li>morphology - shaft </li></ul><ul><ul><li>cuticle </li></ul></ul><ul><ul><ul><li>scale structure covering the exterior of the hair </li></ul></ul></ul><ul><ul><ul><li>scales always point to tip of hair </li></ul></ul></ul><ul><ul><ul><li>scale pattern often used for species identification </li></ul></ul></ul>
  14. 15. Hair <ul><li>morphology - shaft </li></ul><ul><ul><li>cortex </li></ul></ul><ul><ul><ul><li>main body of the hair shaft </li></ul></ul></ul><ul><ul><ul><li>pigment giving hair its color is embedded in the cortex </li></ul></ul></ul><ul><ul><ul><ul><li>lack of pigment = gray or white </li></ul></ul></ul></ul><ul><ul><ul><ul><li>number, shape and distribution of pigment granules can be used to narrow down class </li></ul></ul></ul></ul>
  15. 16. Hair <ul><li>morphology - shaft </li></ul><ul><ul><li>medulla </li></ul></ul><ul><ul><ul><li>may appear dark or translucent depending on substances inside </li></ul></ul></ul><ul><ul><ul><li>can be continuous, interrupted or fragmented </li></ul></ul></ul><ul><ul><ul><li>also used to identify to species </li></ul></ul></ul><ul><ul><li>medullary index </li></ul></ul><ul><ul><ul><li>measures diameter of medulla relative to diameter of hair shaft </li></ul></ul></ul><ul><ul><ul><li>humans usu. less than 1/3, animals usu. more than ½ </li></ul></ul></ul>
  16. 17. Hair <ul><li>morphology - root </li></ul><ul><ul><li>located in hair follicle of skin </li></ul></ul><ul><ul><li>three stages of growth </li></ul></ul><ul><ul><ul><li>anagen phase: major growth </li></ul></ul></ul><ul><ul><ul><li>catagen phase: intermediate </li></ul></ul></ul><ul><ul><ul><li>telogen phase: mature hair – will “fall” out </li></ul></ul></ul>
  17. 18. Hair <ul><li>morphology - root </li></ul><ul><ul><li>telogen </li></ul></ul><ul><ul><ul><li>naturally shed hairs, such as a head hair dislodged through combing, display undamaged, club-shaped roots </li></ul></ul></ul>
  18. 19. Hair <ul><li>morphology - root </li></ul><ul><ul><li>anagen or catagen </li></ul></ul><ul><ul><ul><li>a hair forcibly removed from the scalp will exhibit stretching and damage to the root area </li></ul></ul></ul><ul><ul><ul><li>forcibly removed hairs may have tissue attached </li></ul></ul></ul><ul><ul><ul><li>may contain DNA </li></ul></ul></ul>
  19. 20. Hair <ul><li>other </li></ul><ul><ul><li>root is embedded in follicle which is in equalized with the blood supply </li></ul></ul><ul><ul><ul><li>anything taken into the body is distributed into growing hair (drugs, poisons) </li></ul></ul></ul><ul><ul><ul><ul><li>esp. metals like Hg, As, Pb </li></ul></ul></ul></ul><ul><ul><ul><li>time frame can be established as hair grows at a fixed rate </li></ul></ul></ul>

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