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Forensic Examination of Hair

Forensic Examination of Hair. Shengjie Nie Asoc.Prof. Section of Forensic Biology. Hair evidence & criminal investigation. Grows almost everywhere Naturally shed. Be left on clothing or scene unintentionally / force. Small hairs can not escape the prying eyes of an expert. Outline.

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Forensic Examination of Hair

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  1. Forensic Examination of Hair Shengjie Nie Asoc.Prof Section of Forensic Biology

  2. Hair evidence & criminal investigation • Grows almost everywhere • Naturally shed. • Be left on clothing or scene unintentionally / force Small hairs can not escape the prying eyes of an expert.

  3. Outline • Biology features of hair • Introduction • Hair structure • Hair growth • Color & shape • Distribution • Forensic identification • Whether the hair-like evidence in question is hair? • Whether the hair originated from an animal or a human? • Individualize a human hair. • body area? damage? Poison? Biology features of hair

  4. Introduction • produced from hair follicle(毛囊) • develop hair follicles duringfetal development（胎儿发育） • composed of keratin(角蛋白)

  5. Hair structure Hair tip Hair shaft Hair root

  6. Hair shaft 毛干 cortex毛皮质 medulla毛髓质 cuticle 毛小皮 Hair structure

  7. Hair structure

  8. Medulla毛髓质 Filled with liquid Appears translucent 半透明 Filled with air Appears opaque 不透明 Hair structure

  9. Medulla毛髓质 continuous Interrupted Fragmented • Not present in all human hairs • Presence of medulla varies quite a bit: even hair to hair Hair structure

  10. Same hair, different medulla Five regions of a single head hair (from proximal to distal) Hair structure

  11. Ladder like medulla Uniserial Ladder Medulla Multiserial Ladder Medulla Hair structure

  12. Lattice like medulla 晶格状髓质 polyhedral-shaped 多面体 Hair structure

  13. Hair structure Human hair Be continuous or discontinuous. Not large,<1/3 the width of the hair shaft Medulla Animal hair Be continuous. >1/3 the width of the hair shaft Specific pattern cattle deer deer Medulla: important for species identification

  14. Hair cortex 毛皮质 • spindle-shaped cells • parallel to the length of the hair • Embedded with pigment granules 梭形细胞 Hair structure

  15. Hair structure Pigment distribution Uniform distribution Peripheral distribution One-side distribution Central distribution

  16. Human hair Greater than medulla, >1/3 Distribution of pigment: even, slightly more towards cuticle Cortex Animal hair Less than width of medulla,<1/2 Distribution of pigment: Central or denser towards medulla Hair structure

  17. Hair cortex 毛皮质 • The cortex varies in: • Thickness • Texture • Color 纹理 Important for matching. Hair structure

  18. Hair structure Hair cuticle毛小皮 • outer layer of the shaft • overlapping scales • Characteristic: • How many are there per centimeter • How do they overlap • Its overall shape • Its thickness • Whether or not it contains pigment. Important in species distinguishing

  19. Hair structure Spinous Scales 棘状鳞片 Coronal Scales 冠状鳞片 Bat/some other rodent 啮齿类 Cats, seals and mink Mink 水貂 Bat 蝙蝠 Scales are triangular in shape and tend to lift away from the hair at their tips

  20. Hair structure Imbricate Scales 叠瓦状鳞片 Human Scale Pattern ---flattened scales Hair cuticle

  21. Human Hair Vs. Animal Hair

  22. Human Hair Vs. Animal Hair Curticle, cortex and medulla

  23. Hair root 毛根

  24. Hair root Hair bulb 毛球 hair follicle 毛囊 Hair papilla 毛乳头

  25. Hair structure Hair tip cuticle cortex Hair shaft medulla bulb Hair root follicle papilla

  26. Hair Growth 毛发生长 Telogen phase 生长终期 Catagen Phase 生长中期 Anagen Phase 生长初期

  27. Anagen Phase 生长初期 Sheath 毛根鞘 • High metabolic and mitotic activity; 2-6 years • Follicle re-forms. • Need a strong pull to detach them from the papilla. • Roots : appear fleshy, sometimes with pigmentation. • Sheath tissue may be attached.

  28. Catagen Phase 生长中期 No sheath • The inner root sheath begins to disintegrate 蜕变. • Melanin 黑色素 production stops. • The hair gradually stops growing； 2 to 3 weeks. • Hairs stay attached to the remains of the follicle • Appears brush-like but with no sheath adhering

  29. Telogen phase 生长终期 • Follicle is very short , the papilla is separated. • Mitotically inert and contain less DNA. • Lasts for 3-4 months. • No sheath attached, little or no pigment. • Telogen finishes when a new anagen phase commences.

  30. Hair color & hair shape Influenced heavily by genes. Intentional alteration (perming烫/dyeing) can affect the physical appearance

  31. The distribution of hair 毛发分布 Pubic 阴毛 Limb 腿毛 Beard 胡须 continuous double medulla trace medulla,soft Stiff , curl • Except for the lip, palm, footplate, finger and toes. • The body area determined by the length, shape, color, stiffness, curliness, microscopic appearance.

  32. Which is human Hair ? B C C A

  33. Which is human Hair ? A C B B D

  34. Which phase? Naturally shed or Forcibly removed? C B A Anagen Phase Telogen Phase Catagen Phase Forcibly removed hairs Exhibit stretching and damage to the root area Naturally shed hairs, Undamaged, club-shaped roots. Forcibly removed hairs Tissue attached

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