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Hair

Hair. Forensics. Hair is physical evidence. Forensic characteristics of hair: Color Structure Morphology It is not possible to individualize human hair. Structure of Hair. Hair is an appendage of the skin Hair grows out of the hair follicle organ

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Hair

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  1. Hair Forensics

  2. Hair is physical evidence • Forensic characteristics of hair: • Color • Structure • Morphology • It is not possible to individualize human hair

  3. Structure of Hair • Hair is an appendage of the skin • Hair grows out of the hair follicle organ • The hair extends from the root embedded in the follicle, continues into a shaft and terminates at the tip end

  4. Hair Identification • Important features: • Cuticle scale structure • Medullary index • Medullary shape • Other features: color, length, diameter; distribution, shape, color intensity of pigments • Comparison microscope is an invaluable tool

  5. Hair Shaft • Used for most intense examination • Composed of 3 layers • Cuticle • Cortex • Medulla

  6. Cuticle • Outside covering of the hair • Makes hair resistant to chemical decomposition and makes it able to retain structural features over time • Structure: • Overlapping scales that point towards the tip end of each hair • Different species have different scale patterns

  7. Cuticle • View the cuticle with a: • Scanning electron microscope • Cast of the hair’s surface and view under a compound microscope

  8. Cuticle – Scale Patterns • 3 types of patterns • Coronal: small rodents and bats but rarely in human hairs • Spinous: mink, seals, cats, and are never found in humans • Imbricate: human hairs and many animal hairs

  9. Cuticle – Scale Pattern • Rabbit

  10. Cuticle – Scale Pattern • Deer

  11. Cuticle – Scale Patterns • Human

  12. Cuticle – Scale Patterns • Dog

  13. Cuticle – Scale Patterns • Cat

  14. Cuticle – Scale Patterns • Mouse

  15. Medulla • Looks like the central canal running through a hair • More than half of the hair’s diameter • Medullary index: measure of the diameter of the medulla relative to the diameter of the hair shaft (fraction) • Humans: usually less than 1/3 • Most other animals: ½ or greater • Presence and appearance varies from individual to individual and even among the hairs of a given individual

  16. Human Medullary Index 0.53 nm 1.59 nm

  17. Medulla • 4 ways to classify: • Continuous • Most animals, Some humans (Asians) • Interrupted • Most animals • Fragmented • Humans • Absent • Humans

  18. Medulla • Shape • Cylindrical shape: humans & many animals • Various shapes for some animals • Searchable database for 35 common animal hairs encountered in forensic casework

  19. Medulla - Patterns • Rabbit

  20. Medulla - Patterns • Deer

  21. Medulla - Patterns • Human

  22. Medulla - Patterns • Dog

  23. Medulla - Pattern • Cat

  24. Medulla - Patterns • Mouse

  25. Hair Identification - Race • 1st: Distinguish between animal vs. human • 2nd: Identify race • Asian: wider diameter than the hairs of the other racial groups, thicker cuticle, continuous and wide medulla, larger pigment granules

  26. Hair Identification - Race • African: largest pigment granules and are grouped in clumps of different sizes and shapes. • Caucasian: evenly distributed pigment granules.

  27. Hair Identification – Body Area • Head: uniform diameter and usually a cut tip • Pubic hair: coarse and wiry, exhibit considerable diameter variation or buckling, often have a continuous to discontinuous medulla

  28. Root • Shows if hair was removed with force

  29. Can we tell if hair was dyed? • Yes! • Color will appear in cuticle and cortex • Bleach removes pigment • Estimate time since dyeing or bleaching: • Hair grows at approximately 1 cm per month

  30. Damaged Hair

  31. Special Characteristics

  32. Collection & Packaging • Collect at least 50 full length head hairs from all over the scalp • Collect at least 24 full length pubic hairs from all pubic areas • Method: Pull hair out of skin, clip near skin line, or vacuum up

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