CJO3 EOC Review Hairs and Fibers

O – Describe hair and fiber identification procedures

What are the components of hair? O Follicle – Club-shaped structure embedded in the skin O Shaft – Produced by the follicle

What are the layers of the hair shaft? O Medulla – Innermost, hollow tube or filled with cells O Cortex – Middle, largest part, contains most of the pigment O Cuticle – Outermost, transparent and made of overlapping scales, protects inner layers

What type of evidence is hair? O Class – If follicle is not attached O Individual – If follicle is attached O DNA can be found in the follicle and an analysis could be completed

How is a toxin analysis completed on hair? O The distance the toxin appears from the root of the hair is divided by 1.3cm (growth rate) O The resulting number provides an estimate of the number of months since the toxin was ingested

How are fibers classified? O As natural or synthetic

What are characteristics of natural fibers? O Come from animals, plants, and minerals O Include hair, fur, and webbing O Can be produced by seeds, stems, roots, and leaves O The plant variety shares the common polymer cellulose O Were used primarily, until the 19 th century, to make clothing and textiles O Weaker O Damaged by microorganisms O Melt at a higher temperature

What are characteristics of synthetic fibers? O Man-made O Categorized as regenerated fibers and polymers O Include rayon, acetate, nylon, acrylics, and polyesters O Easily distinguishable in a forensics lab O Stronger O Not damaged by microorganisms O Deteriorate in bright sunlight and melt at a lower temperature

How can you tell if trace evidence is a hair or fiber? O Look for the presence of a medulla O Calculate the medullary index (ratio of medulla diameter to the shaft diameter) O 0.5 or greater = Animal hair or natural fiber O 0.33 or less = Human hair