by Tricia Psarreas Murray

Created on: June 13, 2009

Hair and fiber evidence can be critical to an investigation. In most circumstances, these alone cannot provide a positive identification of a suspect, but these laboratory techniques can be extremely helpful in narrowing down a list of suspects. When dealing with these types of evidence, it is imperative to follow proper procedure. Failing to follow protocol could seriously lower the chances of finding a suspect.

When collecting hair evidence, it is extremely important to make sure that all standard or reference hairs come from the same area of the body. This is because the physical characteristics of hair differ greatly in different parts of the body. If a person tries to compare head hair to pubic hair, for instance, a match will probably not be made.

Most hair comparisons deal with either head or pubic hair. If collecting head hair, a representative sampling can usually by obtained with about 50 full-length hairs. Approximately two dozen full-length pubic hairs are needed for a good sample. It is necessary to collect the entire length of each strand of hair, because a hair can show variation in color or other physical characteristics throughout the strand. If either the size of the collection or the length of each piece of hair falls below the minimum, it can be very difficult or impossible to form any connections based on these pieces of evidence.

When collecting fibers, careful examination of all fiber carriers is imperative. As this evidence cannot usually be seen with the naked eye, it is important to have somebody at the scene to specifically look for these clues. Each piece of clothing that could contain relevant fibers should be bagged separately in paper bags. Every item must be bagged separately to avoid the chance of cross-contaminating the evidence. Likewise, all articles such as carpets, rugs, and bedding should be individually folded and packaged to protect fiber evidence. If a fiber must be removed to keep it best preserved, it should be removed with forceps and placed in a small sheet of paper. Once that has been folded and labeled, it should be put in another container for safekeeping. The importance of properly collecting and preserving fibers cannot be stressed enough, as failure to follow necessary procedures could highly contaminate the evidence. This, in turn, can highly decrease the chances of finding the critical evidence needed for solving a case.

There are many techniques used to analyze hair and fiber evidence.

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