The Utilization of Microscopy in Developing Investigative Leads from the Examination of Microscopic Trace Evidence in Forensic Investigations

The majority of trace evidence examinations, performed in laboratories of forensic science throughout the world, are of a comparative nature. Questioned (Q) items of evidence (e.g., fibers, hair, glass, paint, soil) from a crime scene (or victim, suspect, location, etc.) are compared to suspected items of known (K) origin to determine the likelihood that the K and Q items could have originated from the same source. The justification normally invoked for performing these comparisons is Locard's Exchange Principle, which states that whenever two objects come into contact there is a transfer of material between them. The original research into the analysis of dust traces, which led Nickolls 1 in 1956 to recognize and name this principle, was performed by Edmond Locard between 1910 and 1965. Since then, this principle has been repeatedly validated by means of published research and casework. The research reports describe the results of transfer experiments, most often with fibers, performed by forensic scientists from around the world. The results of these experiments have all confirmed Locard's original premise. Published casework reports also confirm the utility and value of microscopic traces in demonstrating contact between individuals, vehicles, sites, etc., to events in question, even when no eye witnesses were present to give testimony.