Fiber Analysis
Fibers are among the most commonly transferred and recovered trace evidence. They are classified as natural (cotton, wool, silk) or manufactured (polyester, nylon, acrylic, rayon). Forensic fiber analysis proceeds from general to specific: visual examination (color, length, diameter), stereomicroscopy (surface texture, cross-sectional shape—round, trilobal, dog-bone), polarized light microscopy (birefringence patterns identifying polymer type), fluorescence microscopy (dye characteristics under different wavelengths), and microspectrophotometry (precise color measurement enabling objective comparison). Advanced techniques include FTIR (Fourier Transform Infrared Spectroscopy) for polymer identification and pyrolysis-GC/MS for detailed chemical characterization. A single fiber match does not prove contact—the evidential weight depends on fiber type rarity, color uniqueness, and the number of matching fibers recovered.