Hairs and Fibers - Forensic Science - Lecture Slides, Slides of Forensics

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*The value of the evidence depends on the

uniqueness of the fiber

*Rare fibers are more valuable

*Questions to ask

*What type of fiber is this?

*What color?

*How many fibers were found?

*Exactly where was it found?

* What kind of textile did it come from?

*What type of crime was committed?

*Were multiple types of fibers transferred?

*How much time has elapsed?

*What common police practice was stopped

because of fiber transfer?

* Fibers are the smallest unit of a textile.

*When fibers are spun together they make a

yarn.

* Textiles are things like clothing, carpets, and

upholsteries. Textiles are made by weaving yarns together.

*Fibers can be classified as:

*Natural

* Come from animals, plants, and minerals that are

mined from the ground

*Synthetic

* Man-made

*Began in the 19

th century

*Half of all fabrics today are produced with

synthetic fibers

*Categories

*Modified natural fibers (regenerated)

* Ex: Rayon

*Synthetic Polymer

* Made from petroleum products

* Ex: Polyester, nylon, acrylic, or olefins

Fibers under a microscope

*Synthetic fibers are stronger than natural

fibers and are not damaged by microorganisms

*Natural fibers don't break down in the sun and

can withstand higher temperatures.

*Hair is a form of class evidence unless the

follicle is still attached and DNA can be recovered.

*Good for excluding suspects.

*Transferred very easily.

*Secondary transfer is common with pet hair

*Consists of a follicle and a shaft

*Composed of keratin (a protein) which causes

it to be strong and flexible.

• What are the sebaceous gland and papilla?

*Three layers:

*Cuticle (outer layer)

*Cortex (middle layer)

*Medulla (inner core)

Humans have imbricate flattened cuticles.