October 28, 2014

Structure of Hair- it is not yet possible to individualize a human hair to a single head or body through its morphology - it can provide strong corroborative evidence for placing an individual at a crime scene

- hair is an appendage of skin that grows out of an organ called the hair follicle

- length of hair extends from its root/bulb, continues into the shaft and ends at the tip end

- shaft has three layer: cuticle, cortex and medulla

October 28, 2014

October 28, 2014

Structure of HairCuticle:

- the scale structure covering the exterior of the hair- provides stability to hair and resistance to chemical decomposition- scales always point towards tip end of hair- scales of most animal hair look like shingles on a roof- can look at scales using a microscope or a cast of hair

3 Main Scale Patterns:- coronal- spinous- imbricate (humans) - has an overlapping narrow ridge

October 28, 2014

October 28, 2014

Structure of HairCortex:

- located within the cuticle- made of cells aligned in a regular array, parallel to the length of the hair- main body of the hair shaft- embedded with the pigment granules that give hair color- vary in color, distribution and shape

October 28, 2014

Structure of HairMedulla:

- a collection of cells running through the center of the hair- medullary index measures the diameter of the medulla relative to the diameter of the hair shaft- for humans, it is generally less than one-third; for mostother animals, it is one-half or greater- varies from individual to individual and among hairs on anindividual- classified as being continuous, interrupted, fragmented orabsent- human head hairs generally have no medullae or fragmented ones (exception is Mongoloid race who usuallyhave continuous medullae)- most animals have medullae that are continuos or interrupted- shape can be cylindrical (humans) or patterned

October 28, 2014

October 28, 2014

October 28, 2014

Structure of HairFollicular Tag:

- a translucent piece of tissue surrounding the hair's shaftnear the root - contains the richest source of DNA associated with hair

October 28, 2014

Identification and Comparison of Hair- prime purpose for examining hair evidence in a lab is to establish if hair is human or animal, or to determine if it compares with hair from a certain individual

- hair of various animals differs enough in structure that theexaminer can usually identify the species

- scale structure, medullary index and medullary shape are important in hair identification

- color, length and diameter are also important when trying to compare hairs from an individual

- can usually determine racial origin of hair, whether or not it has been forcibly removed - cannot determine age unless infant