A majority of the biological evidence collected from crime scenes is material of human origin that may allow for identification of the person or persons involved in the commission of the crime. The availability of powerful and robust DNA typing strategies has made it is possible to ascertain with a high degree of certainty whether the biological evidence collected originated from a particular individual. However, according to Locard's Exchange Principal, there is a bidirectional transfer of material evidence between the crime scene and the individual participants. Some of this material evidence may be of non-human origin and include hairs, fibers, biological fluids, soils, and plant material. The collection, identification, and analysis of this evidence may associate an individual to the crime scene or a victim with a suspect.  Traditionally such evidence has been examined using light microscopy and conventional serological methods. The development of molecular genetic approaches to species identification and individualization of non-human DNA (i.e., animal, plant, microbial) will increase the probative value of such evidence and is the subject of this section.

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