What are the pro’s and con’s of hair fiber evidence vs. other types of physical evidence??
Hair and fiber evidence can be serious to an investigation. In most cases, these alone cannot offer a helpful identification of a suspect, but these laboratory techniques can be helpful in narrowing down a list of suspects. When collecting hair evidence, it is extremely important to make sure that all hairs come from the same area of the body. This is because the physical characteristics of hair differ 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 typical 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 the size or the length of each piece of hair falls below the minimum, it can be very difficult to form any connections based on the evidence. When collecting fibers, careful examination of all fiber carriers is imperative. It is important to have somebody at the scene to specifically look for fiber clues because this kind of evidence cannot be seen with the naked eye. Clothing that could contain fibers should be bagged separately in paper bags. Every item must be bagged separately to avoid the chance of cross-contaminating the evidence. Also all items such as carpets and bedding should be individually folded and packaged to protect fiber evidence. If a fiber must be removed, it should be removed with tongs and placed in a small sheet of paper. Once that has been folded and labeled, it should be put in another container for safekeeping. Failure to follow basic procedures could highly contaminate the evidence and decrease the chances of finding the critical evidence needed for solving a case. There are many techniques used to analyze hair and fiber evidence. One of the most valuable tools in making hair comparisons is a comparison microscope. This allows the examiner to view two samples of hair side by side. This makes it possible to discover any variations or similarities in the microscopic characteristics of the hair. Hair can also be analyzed by using DNA. This is an extremely valuable method of examining this evidence. Whether or not two fibers match can be determined by doing a side-by-side comparison of the samples in question. If the color and diameter do not match while doing a microscopic comparison, it is safe to assume that there is no match. If the colors appear to match, the evidence can be highly enhanced by using a visible light micro spectrophotometer. This is a simple way for analysts to separate fiber colors by comparing their shadowy patterns. These methods have been highly successful in narrowing down potential matches, discarding non-matches, and verifying definite matches. It is important to remember that these results can only be achieved if each person on the investigation does his or her part properly. As long as hair and fiber evidence is properly collected and preserved, there is a good chance that the laboratory analysts will be able to use this evidence to discover critical clues about the case.