Criminal Investigations (Narrowing the Field)

While there are limitations on the admissibility of several forms of forensic science in a criminal trial, police can and do use some inadmissible forensic science techniques for investigative purposes. Many pattern identification procedures, such as fingerprints, footwear, microscopic hair analysis, or even bite marks, can effectively exclude possible suspects and narrow the field for further investigation. Polygraphs are also used to implicate or eliminate suspects. Other techniques can provide enough information to pursue a warrant for admissible evidence. Facial recognition software has inherent difficulties but can be an effective initial investigation tool. Genetic genealogy, combining DNA and genealogical information, has become a very effective investigation technique. While its results are not admissible, it can lead police to a suspect from whom they can usually obtain discarded confirming DNA samples.