Most individuals can lose up to 100 (or more) head hairs naturally per day. Hair examinations can be used to evaluate various morphological features of a hair, which can determine if a hair is human, animal, or synthetic in origin. Animal hair can be evaluated to determine the species of origin. Human hair can be evaluated for body area, length, root condition (shed/forcibly removed), artificial treatment, damage, decomposition, and suitability for nuclear or mitochondrial DNA analysis. Comparison of microscopical characteristics of human hair can aid in determining if a person can be included as a possible source of a questioned hair, but cannot provide a personal identification.
A fiber is the smallest unit of a textile material that has a length many times greater than its diameter. Fibers are prevalent in our daily lives and have a high chance of being transferred during a crime. Fiber examinations can evaluate if the fiber is natural or synthetic. A variety of analytical techniques (various microscopical methods, Fourier Transform Infrared Spectrophotometry, Raman Spectrophotometry, Melting Point Evaluation, Pyrolysis Gas Chromatograph Mass Spectrometer) and physical features can be evaluated to further determine the specific chemical composition of the fiber. Moreover, fibers from an unknown source can be compared to fibers from a known source to determine if they are consistent with having originated from the known source or a different source with similar properties. Multiple fibers from unknown sources may also be compared to each other to determine if they are consistent with originating from the same source, even if the source is unknown. Fibers may be spun with other fibers to form a yarn, which is then woven or knitted to form fabric. Fabric can also be examined and evaluated for color, construction, and fiber composition. Torn fabric can be physically matched to a damaged garment.