The term trace evidence is generally thought of as any type of evidence occurring in sizes so small that it can be transferred or exchanged between surfaces without being noticed.
Whenever two objects come into contact there is always a transfer of material. The methods of detection may not be sensitive enough to demonstrate this or the decay rate may be so rapid that all evidence of transfer has vanished after a given time. Nonetheless, the transfer has taken place. --Edmond Locard
Fiber Comparison, Spandex Fibers Midshaft of human hair
Fiber and textile evidence can provide strong evidence of an association in criminal cases. Examination of evidence for fiber transfer can provide a valuable means of helping to establish association between two or more persons, or between a person and either a crime scene or an object.
Fibers are first classified by being natural or synthetic, and then the type of fiber is determined using polarized light microscopy and Fourier Transform Infrared Spectrometry (FTIR). Other fiber characteristics examined include color and cross-sectional shape.