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