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 Institute for Criminalistics in Lyon, France. This was basically the beginning foundation for Locard’s Exchange Principle. Locard’s Exchange Principle basically states that if two items come in contact with one another, there will be an exchange of some sort. The techniques he taught and learned there proved useful while working as a medical examiner during World War I, he analyzed stains or dirt on fallen soldiers' uniforms to help the French Secret Service determine where and how the men had died (Locard's Exchange Principle." World of Forensic Science. , 2005). Not only was Locard’s system useful during the war, it became very important in what and how evidence is collected at a crime scene. Because he believed there is no way for a crime to be committed without some trace or transfer being left behind, detectives and CSI are taught to look for the smallest sometimes most inconspicuous pieces of evidence.
Trace evidence can come in many forms. The most common types of trace evidence are hair, fingerprints, and biological fluid stains. When collecting hair, especially at a violent crime scene, there are several factors that have to be determined once collected. Some of those being whether or not the samples came from a human or...
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