Forensic Value of Hair

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1 Forensic Value of Hair Hair is class evidence morphorlogy (how it looks), index (how thick the medula is), color Mitochondrial DNA from shaft. All mitochondria comes from egg only, not sperm. So ONLY maternal lineage If hair bulb (root) is present, then can get nuclear (individual DNA) from it

2 Hair is Class evidence ONLY A piece of hair cannot be individualized to a particular head/person Rather it can be characterized and classified Comparative Microscope Allows technician to compare two hairs side by side Comparison Microscope Two matching hairs

3 When is hair evidence important in a case? Animal or Human determination Body area determination Race association with hair

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5 Animal vs Human Hair The medulla is a string of dots in animal hair. humans frequently lack medulla Pigment in animal hair tend to clump, human hair pigments more evenly distributed Animal hair has distinct banding Human hair color is constant throughout MOST IMPORTANT animal medulla is pretty thick, while in humans the medulla is thin or lacking

6 The Medulla Index is the ratio of the medulla width to the entire hair width. It is much bigger in animals than in humans Human hair Dog hair

7 Animals have a more patterned medulla than humans

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10 HUMAN HAIR The root is club-shaped Consistent in color and pigmentation throughout the length of the hair Medullary index is less than 1/3 Pigment is evenly distributed, slightly more dense near the cuticle

11 Pigment Distribution in Human Hair Brown Human Hair Pigment granules are small, dark, and solid structures They vary in color, size, and distribution in a single hair. In humans, pigment granules are commonly distributed toward the outer edge of cortex The exception is red-haired individuals, granules are concentrated along the center of the hair Red Human Hair

12 Ovoid bodies found in Dog Hair

13 Ovoid bodies are abundant in Cattle hair

14 The cuticle scales are very distinct from species to species

15 A species is defined as organisms that can interbreed and produce fertile offspring

16 Rabbit Spinous cuticle pattern

17 Can you identify the animal hairs shown? Think About It (1) In which samples are we viewing the cuticle? How do they compare? (2) In which samples are we viewing the medulla? How do they compare? (3) What characteristics can be used to identify hair samples?

18 Types of Animal Hairs - Key Cat Horse Pig Human A B C D G E F H Deer Dog Rabbit Rat I Human

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24 Hairs might show signs of cutting Which hair was cut by a razor? Which was cut with scissors? Which split on its own?

25 Pubic Hairs One of the kinds of evidence where the mere presence will suggest foul play.

26 Pubic Hairs Coarse, Wiry Diameter s show a lot of variation Buckling and tapered ends are common

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28 Racial Type of Hair Compare these cross-sections of three hairs, all of different racial types: (left) Asian, (center) Caucasoid, (right) African

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30 African-Origin Hair Shaft diameter: moderate to fine with considerable variation Pigment granules: densely distributed (hair shaft may be opaque) and arranged in prominent clumps Shaft: prominent twist and curl

31 Asian-Origin Hair Shaft diameter: coarse and usually with little or no variation Pigment granules: densely distributed and often arranged in large patchy areas or streaks Medulla: prominent (often broad and continuous) Cuticle: thick

32 Caucasian-Origin Hair Shaft diameter: moderate with minimal variation (mean diameter for human head hairs - 80um) Pigment granules: sparse to moderately dense with fairly even distribution

33 Epidermis - protects skin, renewed frequently Sebaceous gland, sebum, lubricates and waterproofs skin and hair, mostly on face and scalp, not palms or soles All the blood supply to the hair comes from the bottom portion of the hair in the dermis.