DNA analysis is a powerful tool as each person’s DNA is unique (except in the case of of identical twins). Therefore, DNA evidence collected from a crime scene can implicate or eliminate a suspect. It also can analyze unidentified remains through comparisons with DNA from relatives. Also, when evidence from one crime scene is compared with evidence from another, those crime scenes can be linked to the same perpetrator locally, statewide, and nationally.
DNA is also a powerful tool because when biological evidence from crime scenes is collected and stored properly, forensically valuable DNA can be found on evidence that may be decades old. Therefore, old cases that were previously considered unsolvable may contain valuable DNA evidence capable of identifying the perpetrator.
DNA is often compared with fingerprints in the way matches are determined. When using either DNA or fingerprints to identify a suspect, the evidence collected from the crime scene is compared with a “known” standard. If identifying features are the same, the DNA or fingerprint can be determined to be a match. However, if identifying features of the DNA profile or fingerprint are different from the known standard, it can be determined that it did not come from that known individual.
(Information provided by the Department of Justice)