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
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
When is hair evidence important in a case? Animal or Human determination Body area determination Race association with hair
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
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
Animals have a more patterned medulla than humans
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
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
Ovoid bodies found in Dog Hair
Ovoid bodies are abundant in Cattle hair
The cuticle scales are very distinct from species to species
A species is defined as organisms that can interbreed and produce fertile offspring
Rabbit Spinous cuticle pattern
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?
Types of Animal Hairs - Key Cat Horse Pig Human A B C D G E F H Deer Dog Rabbit Rat I Human
Hairs might show signs of cutting Which hair was cut by a razor? Which was cut with scissors? Which split on its own?
Pubic Hairs One of the kinds of evidence where the mere presence will suggest foul play.
Pubic Hairs Coarse, Wiry Diameter s show a lot of variation Buckling and tapered ends are common
Racial Type of Hair Compare these cross-sections of three hairs, all of different racial types: (left) Asian, (center) Caucasoid, (right) African
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
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
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
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.