Trace

Trace Evidence

Mission

The Trace Evidence Unit (TEU) identifies and compares specific types of trace materials that could be transferred during the commission of a violent crime. These trace materials include human hair, animal hair, textile fibers and fabric, rope, feathers, wood, soil, glass, and building materials. The physical contact between a suspect and a victim can result in the transfer of trace materials. The identification and comparison of these materials can often link a suspect to a crime scene or to physical contact with another individual. Torn pieces of fabric can be positively associated to a damaged garment, and broken pieces of glass or wood can be positively fit together. Physical anthropology (skeletal remains) examinations are also performed. These examinations are conducted to assist in the identification of human remains.

The Team

Physical scientist, geologist, and forensic examiners

The Work

The unit maintains reference collections of human and animal hair, natural and man-made textile fibers, fabrics, feathers and wood.

Hair

Hair examinations can determine if a hair is animal or human. If animal, the species and possibly breed of the animal can be determined. If human, the race, body area, length, root type (naturally shed/forcibly removed), and any artificial treatment, damage, or disease can be determined. Hairs associated by microscopic comparison are also examined by the Mitochondrial DNA Unit.

Fibers

Fiber examinations can determine if a fiber is natural or manmade. Questioned fibers can be compared to fibers from a known source to determine if they are consistent with having originated from that source. Questioned fibers can also be compared to other questioned fibers to determine if they are consistent with originating from the same source, though that source is not known.

Fabric

Fabric examinations can determine if a questioned piece of fabric and a known piece of fabric are consistent in color, construction, and composition. Fabric matches may also be done that can positively associate the questioned and known pieces.

Feathers

Feather examinations can determine the species of bird that a feather came from, and questioned and known samples of feathers can be compared.

Wood

Wood examinations can determine the species of wood, compare questioned and known samples of wood, and do fracture and cut end matches.

Other

Additional examinations undertaken in the unit include: cordage, glass, soil, anthropological, building material, and gemstone examinations.