Trace Evidence

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Trace or transfer evidence can be any small, and to the untrained be a seemingly insignificant piece of material, whether man-made or natural, that has been left at a crime scene. Edmond Locard, founder of the Institute of Criminalistics at the University of Lyon, France, developed what has become known as Locard’s Exchange Principle. This states that every contact leaves a trace (Trace Evidence). Trace evidence can consist of just about anything. Some types of trace evidence include but are not limited to hair, blood and other body fluids, paint, glass, and residues. Throughout the years, trace evidence has become very important in the conviction and even the exoneration of those accused of certain crimes.
In 1910 Locard founded the
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Sperm or semen evidence at a crime scene is usually evidence of a suspected sexual assault. As with bloodstain evidence, semen evidence can also help in identifying perpetrators. Saliva evidence cannot usually be seen from visual examination. Saliva evidence is usually retrieved from another piece of evidence such as cigarette butts, gummed surfaces of envelopes, chewing gum, bite marks, ski and/or nylon masks. Saliva evidence can also be useful in helping to find a suspect. Once it is determined that bio evidence is present, if the object containing the biological fluid can be taken in whole to be processed, it is bagged and labeled as usual. However, if the evidence is on something that cannot be transported, then a swab is taken to gather a sample.
The proper gathering, handling and processing of trace evidence is a vital part of any investigation. Because not all cases are cut and dry, the criminals are not caught in the act, having the proper evidence can speak volumes. As stated previously, hair, fingerprints, and biological fluid stains are just some of the common types of trace evidence however, as technology continues to push forward, more and more evidence and ways of testing is coming to light.


Locard 's Exchange Principle." World of Forensic Science. . (2005). Retrieved from
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