UC Davis

A fiber population study is conducted to assess the prevalence of the color and type of fibers present in a certain area to understand what are common fibers and what are rare fibers. This can help investigators determine the evidentiary value of trace fibers as those that are rare would be less likely to be observed in a large quantity unless they came from a specific contact. This study looked at the trace fibers on a military base to create a trace fiber population profile and to determine how the population frequencies differ from previous studies, due to the prevalence of uniforms worn. In previous research, white/colorless, black/grey, and blue were consistently the most common colors observed with yellow, purple, and orange as the rarest. Cotton was consistently the most common type, manufactured fibers have become increasingly popular, and in almost all cases, animal-based fibers were rare. Nearly 22,000 fibers were collected via a tape lift from 25 fabric-covered chair seats in a lobby area on Beale Air Force Base and subsequently examined using a microscope to determine their apparent colors. Overall, blue and white/colorless were the most common colors observed (32.0% and 31.5%, respectively) and orange, purple, and green were the least common (0.5%, 0.3%, and 0.3%, respectively). Rare color fibers were then assessed to determine their fiber type. From those rare colors, plant-based fibers were most common (77.7%), followed by synthetics (17.4%), and finally animal-based (5.0%). These findings were comparable to previous studies conducted and suggest that the prevalence of uniforms on the military base did not significantly contribute to the trace fiber population. It is possible that the uniform fabrics do not shed much due to their composition which would result in there not being an increase in those colors in the trace fiber population. It can be useful for investigators to note that the clothing worn in a specific area will not necessarily determine what fibers are common or rare in trace amounts. A fiber may have more value than assumed based on looking at the textiles common to the area.