Ch. 4 Fibers Casey Anthony (fiber/duct tape)Casey Anthony (fiber/duct tape) beginning and 6 ½ min in Saferstein and TraceSaferstein and Trace (several min in)

Fibers The value of fibers as evidence depends on narrowing their origin to a limited number of sources. Fibers are a form of trace evidence that is transferred between individuals and objects during a crime- used to corroborate other evidence that is found

Important in these types of cases: Homicide Assault Sexual offense (transfer between people) Hit and run (fibers adhere to vehicle)

Types of Transfer Direct Transfer: passes directly from object to victim or vice-versa Secondary Transfer: transfer from a source to a person then onto another person

Problems: Mass production of our garments Need to calculate probabilities of how many people would own that fiber Early collection is critical, w/in 24 hours 95% of all fibers will have fallen from victim or lost from scene

Types of Fibers: Natural ( depends on color and morphology) 1. Animal Hair: Sheep, goats, camels, muskrat (Use animal hair ID methods) Webbing: silk (from caterpillar cocoons) llamas, alpacas, woven into textiles Fur: mink, rabbit, beaver

2. Plant Seed Fiber : Cotton cellulose(has ribbon like twists at irregular intervals, Dyed cotton provides more evidential value than white cotton) Fruit Fiber: coir- fibers on coconut shell (used for doormats, baskets) Stem Fiber – jute, hemp, flax (linen) Mineral Fiber – fiberglass, asbestos

Man-Made Increase in amount since 1930’s 1000’s of fibers under diff. Trademarks Get regenerated or synthetic Regenerated fibers: made from natural raw materials (ex. Rayon  cellulose & nitric acid), made by forcing material thru holes of spinnerets

Synthetic Polymers Synthetic man-made fibers Made thru polymerization Ex. Nylon (1 st marketed synthetic polymer), polyester, acrylics, olefins How is Polyester made?

Analyzing Fibers Look at: Type of fiber Fiber color # of fibers found Where they were found, Textile it originated from Type of crime committed Time between crime and discovery of fibers

Types of Instruments Used: Infrared Spectrophotometer- Measures the quantity of radiation that a particular material absorbs Microspectrophotometer - Spectrophotometer w/ a light microscope attached (get spectrum analysis also)- 1500x Polarizing Microscope -Study materials that have double indices of refraction (birefrigence)

Aspirin

Microspectrophotometer

Identification & Comparison of Man-made fibers Fibers are class evidence, forensic significance depends on location, number & nature of fiber Fabrics that can be exactly fitted together are of obvious common origin Common analysis: side by side comparison of control and crime scene fiber Color & diameter are obvious points of comparison

Other Characteristics: Striations (lengthwise or surface) Delustering agents (TiO 2 -reduces shine) Cross section- see if unusually shaped Weave Pattern - look at the warp/weft (plain, basket, satin, twill, leno) Dye composition- use microspectrophotometer Chemical composition- see what broad class of chemical it belongs to, use infrared spectrophotometer

Polymeric structure (Ex. 200 samples of acrylic fall into 24 diff. Groups) Physical properties: crystallinity,index of refraction, birefringence, polarizing properties, absorbance