Analyzing Fibers Forensic Science

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Presentation transcript:

Analyzing Fibers Forensic Science

Fibers Material composing fabrics and garments Two types: Man-made and Natural

Natural Fibers Derived completely from plant or animal sources Identified by microscopic examination of color and morphology of fiber Most prevalent is cotton

Microscopic Examination of Cotton Under microscope, the cotton looks like twisted ribbon or collapsed and twisted tubes. These twists are called convolutions.

Man-Made Fibers Fibers created from natural or synthetic polymers Dates back to 1911 with rayon and 1939 with nylon Polymers: chains of regular and repeating atoms

Microscopic View of Polyester Smooth fibers with regular diameter. Diameter generally ranges from 12-25 micrometers. The un-dyed fabric is usually off white and transparent.

Comparison and Identification of Fibers Most important is the ability to trace the origin of the fibers Only if pieces completely fit together can a definite origin be determined If cannot fit together, the fibers must be compared side-by-side with standard/reference samples

Comparison and Identification of Fibers (cont’d) First microscopically compare fibers for diameter and color Look for other morphological details like striations or pitting Use visible light microspectrophotometer to analyze colors of fibers for comparison

Collection and Preservation of Fiber Evidence Know potential carriers of fiber evidence Collect and package evidence in separate paper bags Fold blankets, carpets and rugs to prevent loss of evidence Cover car seats with polyethylene sheets