Analyzing Fibers
with
Infrared Spectroscopy
THE ANALYTE: Synthetic Fibers (possibly polyester, nylon, or acrylic...)
THE IDENTITY TEST: The expected identity of the fiber has been established by observing it under a microscope. Now it is tested with IR to confirm the suspected identity.
Single threads of the fiber are put into a machine that shines infrared light on them. The unique chemical structure of compounds within the fiber react to the light; different compounds absorb different wavelengths.
The machine prints out a graph, which the chemist analyzes by comparing the graph to known graphs. The known graphs may be a list of wavelengths in a book, or an integrated, international computer database the matches the graph to an identical or very similar known graph.
THE IDENTITY AND THE CRIME: The fiber has been confirmed as matching fibers found on the crime scene, the victim, or the suspect. Combined with other evidence, the forensic scientist testifies to a judge, district attorney, or jury, and the culprit is prosecuted.
Read about the FBI's Forensic Fiber Guidelines
Chapter 1 (Introduction)
Chapter 2 (Microscopy Textile Fibers)
Chapter 3 (Visible Spectroscopy of Textile Fiber)
Chapter 4(TLC of Dyes in Textile Fibers)
Chapter 5 (PGC of Textile Fibers)
Chapter 6 (IR Analysis of Textile Fibers)
Infrared Spectroscopy |
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