TRACE EVIDENCE: HAIR. Anatomy of a Hair Cortex  Largest portion of the shaft  Contains hair pigment Cuticle  Layer of cells that cover the surface.

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Presentation transcript:

TRACE EVIDENCE: HAIR

Anatomy of a Hair Cortex  Largest portion of the shaft  Contains hair pigment Cuticle  Layer of cells that cover the surface of the shaft  Look like fish scales and have distinct patterns  Coronal (crownlike) – rarely found in humans, common in rodents  Spinous (petallike) – triangular in shape, not found in humans, common in cats  Imbricate (flattened) – found in humans and many other animals Medulla  Central core of the hair  Medullary index is the width of the hair. Animals index is greater than.5, humans.3

Criminologist At the crime scene you can collect hair by  Filter paper on a vacuum cleaner  Tape lifts  Collecting actual samples from victims or suspects (generally collect 50 + hairs)

Criminlogist Compare unknown sample of hair to known samples using a comparison microscope  Color and width  Distribution pattern of the medulla  Color and distribution pattern of pigment in the cortex  Cuticle pattern  Appearance of root tip (damaged could represent struggle)  Tip appearance If root or bulb is found then DNA can be extracted

Criminologist Chemical testing  Chemicals absorbed by skin can be detected in hair shaft  Sectional analysis can establish timeline for exposure to toxins  Neutron Activation Analysis (NAA) read John Vollman case from Forensics for Dummies Page 272