1. Wednesday February 11, 2015
SWBAT investigate famous cases involving hair evidence in order to present them to our class briefly.
Then we will begin our fiber notes
Drill: How did the hair evidence in the Casey Anthony Trial impact the case?

2. Fiber Evidence

3. Natural Fibers - Animal
Derived from plant or animals
Animal fibers comprise a majority of natural fibers found at crime scenes
Examples of Animal Fibers
Sheep (wool)
Goats (mohair, cashmere)
Camels, Llamas, Alpacas
Fur Fibers - Mink, Rabbit, Beaver, Muskrat

4. Natural Fibers - Plant Cotton is the most prevalent plant fiber
White cotton fibers have no evidential value because it is so common

5. Two Types of Man-made Fibers
Regenerated Fibers
Made from natural raw materials
Examples:
Rayon
Acetate
Triacetate
Synthetic Fibers
Made solely from synthetic chemicals
Examples:
Nylon
Polyester
Acrylics

6. Man-Made Fibers Rayon developed 1911 Nylon developed 1939
Today these fibers are prevalent and produced under a variety of names

7. Man-Made Fibers
Man-made fibers are made by pulling a synthetic material into thin strands
The synthetic material is a polymer
A polymer is a chain of repeating units (monomers)

8. Forensic Identification
Naked-eye comparison of striations and pitting on surface of fibers
Microscope comparison for color and diameter
Match torn edges together
Matched torn edges together is a virtual certainty that the fabrics were of common origin

9. Chemical Analysis – IR
Chemical analysis of dyes in the fabric
Infrared spectroscopy
Compositional differences in the dyes can distinguish fibers
Fibers will absorb infrared light in a characteristic pattern
Infrared Spectrophotometry can identify generic classes and subclasses of fibers
Does not destroy or damage the fiber

10. IR Spectroscopy

11. Chemical Analysis – Burn Test
To determine if the fabric is natural, man-made, or a blend
Cotton: steady flame, smells like burning leaves
Silk: burns readily and smells like burning hair, leaves crumbled ash behind
Wool: similar to silk, but harder to ignite
Polyester: melts
Rayon: burns rapidly and leaves only slight ash
Silk and wool are protein fibers

12. Collection & Packaging
When collecting sample clothing, it is vital that no two articles come in contact with each other
If the sample is dry, it can be packaged in a pharmacy fold or plastic vial
If the garment is wet it should be air-dried and then placed in a paper bag