FBI Information: "Hair, Fibers, Crime & Evidence" This link opens in a new windowThe investigation and successful prosecution of individuals suspected of involvement in violent crimes often includes the identification and comparison of trace evidence. Trace evidence consists of materials or substances that are generally small in size and may be transferred when physical contact occurs between two individuals, between an individual and an object, or between two objects. Included in this evidence are hairs, textile fibers, soil, glass particles, paint chips, feather fragments, explosive residues, and other materials. Crimes that often result in these types of transfers include homicides, sexual assaults, aggravated assaults, and hit-and-run incidents.