Forensic Lab Investigations

Hair Analysis What Is Hair? What Is Hair? Produced by hair follicle Produced by hair follicle Consists of: Consists of: Shaft (projects from skin) and a root (embedded in the follicle) Shaft (projects from skin) and a root (embedded in the follicle) Shaft is flat and ribbon-like in cross-section – curly hair Shaft is flat and ribbon-like in cross-section – curly hair Oval shaft – wavy hair Oval shaft – wavy hair Round shaft – straight hair Round shaft – straight hair

Hair Analysis Three layers of protein: Three layers of protein: Medulla – center section made of large cells separated by air spaces Medulla – center section made of large cells separated by air spaces Cortex – surrounds medulla; bulky with several layers of flattened cells Cortex – surrounds medulla; bulky with several layers of flattened cells Cuticle – outermost layer, looks like shingled roof Cuticle – outermost layer, looks like shingled roof Greatest source of strength Greatest source of strength Contains pigments – small, dark, and solid structures that are granular in appearance Contains pigments – small, dark, and solid structures that are granular in appearance

Hair Analysis Hair Types: Hair Types: Scalp – uniform Scalp – uniform Beard – coarse, curved Beard – coarse, curved Eyebrow, nose, ear, eyelid – shorter and stubbier, wide medullas; taper at end Eyebrow, nose, ear, eyelid – shorter and stubbier, wide medullas; taper at end Axillary – uneven pigments; fine point at end Axillary – uneven pigments; fine point at end How did it come out? How did it come out? Fell out – bulblike root Fell out – bulblike root Pulled out – sheath attached to bulb or mutilated appearance Pulled out – sheath attached to bulb or mutilated appearance

Scale Pattern: Human Hair

Hair Analysis Hair Identification: Animal Versus Human Hairs Hair Identification: Animal Versus Human Hairs Pigmentation Pigmentation Human Hairs are consistent in color and pigmentation Human Hairs are consistent in color and pigmentation Pigmentation is evenly distributed, or slightly more dense toward the cuticle Pigmentation is evenly distributed, or slightly more dense toward the cuticle Animal hairs exhibit radical color changes Animal hairs exhibit radical color changes Pigmentation is more centrally distributed, more dense toward the medulla Pigmentation is more centrally distributed, more dense toward the medulla Medulla Medulla In human hairs, has a width that is generally less than one- third the overall diameter of the hair shaft In human hairs, has a width that is generally less than one- third the overall diameter of the hair shaft In animal hairs, generally occupies an area of greater than one-third the overall diameter of the hair shaft In animal hairs, generally occupies an area of greater than one-third the overall diameter of the hair shaft Root Root Human hairs roots commonly club-shaped Human hairs roots commonly club-shaped Animal hairs roots highly variable Animal hairs roots highly variable

Pigment in Animal Hair

Human Hair: Root

Hair Analysis Microscopic Examination Microscopic Examination Why Examine? Why Examine? Decays slowly compared to tissues and fluids Decays slowly compared to tissues and fluids May have to compare hundreds of samples May have to compare hundreds of samples Indicate physical contact Indicate physical contact

Hair Analysis What information can a forensic scientist obtain from a hair sample? What information can a forensic scientist obtain from a hair sample? The source (human or animal) The source (human or animal) The age The age Hair pulled out or fell out Hair pulled out or fell out Treatment of hair Treatment of hair Indicates if bleached or dyed Indicates if bleached or dyed Dyed have less prominent pigment granules Dyed have less prominent pigment granules Hair grows about ½ inch per month Hair grows about ½ inch per month What part of body What part of body Drugs, soil, lice Drugs, soil, lice DNA analysis DNA analysis

Human Hair: Brown vs. Red

Human Hair Types

Limb Hair versus Facial Hair

Differences in Hair

Hair Cut Types: RoundedCut BrokenWorn Razor Abraded

Dyed Hair