Fiber Analysis

Where they come from

• Cross transfers of fiber often occur in cases in which there is
• person-to-person contact
• and investigators hope that fiber traceable back to the offender can be found
• at the crime scene, as well as vice versa

Fiber = Class Evidence

• Unlike DNA evidence, fibers are not unique
• Cannot pinpoint an offender in any definitive way
• Only helps narrow down a case, not exactly solve one.

Fiber Acquisition

• Gathered with tweezers, tape, or a vacuum.
• Generally come from clothing, drapery, wigs, furniture, and blankets
• analyzed for determination to be natural, manufactured, or mix of both

Types of Fibers

• Natural: Plants (cotton) or animals (wool)
• Manufactured: synthetics like rayon, acetate, and polyester
• ------> made up of molecules called polymers

Limitations

• Analyst can only work with a certain number of samples
• Evidence collected at scene is compared to examples of suspect evidence
• Car/home fibers laid out side by side for analysis

TOOLS TO ANALYZE

• Compound, Phase-Contrast, & Electron Microscope
• Spectrometer, Spectrophotometer
• Combination of both: Microspectrophotometer

Steps of Analysis

• Color and Diameter
• Chromatography
• Structure
• In short, compares shape, dye content, shape & composition

WAYNE WILLIAMS CASE

• Basically came down to fiber evidence
• Investigators found many errors
• "Matching" fibers were taken only from victims
• Not on fiber was found anywhere near the carpet in the Williams' house

Errors in Prosecution's Judgement

• ignored the fact that same carpet was in all but 2 rooms
• Wayne's room was falsely identified
• Fibers taken as evidence were severely labeled as class and not specific to the Williams'
• Only chose fibers of carpets in houses, disregarding apartments or businesses
• millions of pounds of the same exact fiber had been sold to other businesses

Fiber Probability

• 4 suspects instead of one (all residents of the Williams household)
• fibers could have been mixed from a laundromat
• There were no eyewitnesses, weapon, motive, or confessions from Williams
• Only evidence was trace fibers that solely convicted the suspect
• Clearly the fiber probability ratio was not as impressive as it seemed.