FIBERS

ROLE OF FIBERS AT CRIME SCENE

• Fibers are found mostly in cases where there has been person to person contact
• Investigators hope that the fiber found can be traced back to the offender
• The success of solving a crime using fibers as evidence often depends -
• - on the ability to narrow down the source for the type of fibers found

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NEGATIVE TO FIBER EVIDENCE

• Not unique
• Cannot pinpoint an offender in any definitive manner
• There must be other factors involved such as evidence that the fibers -
• - can confirm something unique to the fibers that set them apart

FIBERS AT A CRIME SCENE

• Gathered with tweezers, tape or vaccum
• Generally come from clothing, drapery, wigs, carpeting, furniture or blankets
• Whatever is gathered at the crime scene is compared against fibers from the suspect -
• - and are laid side by side for visual inspection through a microscope

TYPES OF FIBERS

• Natural: come from plants (cotton), or animals (wool)
• Manufactured: synthetics like rayon, acetate, and polyester -
• - made from long chains of polymers

MICROSCOPES

• Used to determine the shape and color of fibers
• Compound microscope uses light reflected from the surface of a -
• - fiber and magnified through a series of lenses
• Comparison microscope is used for more precise identification
• Phase-contrast microscope reveals some of the structure of a fiber

spectrometer

• Separates light into component wavelengths
• By passing light through something to produce a spectrum, the analyst -
• - can read the resulting lines, called "absorption lines
• Measures light intensities, to identify different types of substances

FIBER ANALYSIS

• The first step is to compare color, shape, size, dye content, -
• - chemical composition and microscope appearances
• No fiber database that provides a probability of origin
• Even if fibers from two separate places can be matched via -
• -comparison, that does not mean they derive from the same source

ERRORS WITH FIBERS IN CASES

• Throughout time there have been mistakes made with fibers in certain cases
• Example: Wayne Williams case, it came down to only fiber evidence
• The main issue was how fiber evidence was presented

MISTAKES MADE IN WILLIAM'S CASE

• Ignored the fact that the same carpet was in all but one or two rooms in the house
• Overlooked the fact that Wayne Williams had changed rooms since last murder
• Included only fibers said to have been used in carpets for residential applications
• Ignored the fact that millions of pounds of the exact same fiber had been -
• - sold undyed to other manufacturers for use in applications