Trace Evidence examination is often challenged in court for its uncertainty. Nonetheless, characterization of hair and fiber evidence has played an important role in providing investigative leads in many criminal cases. It is not to be replaced in its entirety by DNA analysis, but to be used complementarity with other disciplines and technology in forensic science. Just as natural variations in skin ridge patterns and characteristics provide a key to human identification,minute random markings on surfaces can impart individuality to inanimate objects. Structural variations and irregularities caused by scratches, nicks, breaks,and wear permit the criminalist to relate a bullet to a gun; a scratch or abrasion mark to a single tool; or a tire track to a particular automobile. Individualization, so vigorously pursued in all other areas of Criminalistics,is frequently attainable in firearms and tool examination.