A very interesting article on how Evolutionary Theory is used has been posted over at Scientific American. Here's my favorite part:
Evolutionary analyses and criminal investigations hold the same goal of revealing historical events. Their fruitful combination awaited only the maturing of DNA-sequencing technology to provide large data sets, robust quantitative methods, and enlightened integration of science and the legal system.
As with many applications of evolution, the concept of molecular clocks plays a vital role. Changes in many DNA sequences occur at roughly predictable rates over time, forming the basis for molecular clocks. The clocks for two regions of DNA, however, can run at markedly different rates. In the early 1980s geneticists discovered regions of human DNA that evolve very rapidly, and scientists soon pressed these fast-evolving regions into service as genetic markers—unique identifiers of individuals, like fingerprints but with greater detail—in criminal cases and in paternity testing.
Forensic investigators assess specific genetic markers as indicators of links between suspects and crime scene evidence such as a single human hair, lip cells left on a beer can, saliva on envelope flaps and cigarette butts, as well as semen, blood, urine and feces. The most straightforward use is to demonstrate a suspect’s innocence by the nonmatching of his or her markers compared with those of crime scene evidence. Indeed, the Innocence Project, a public policy organization promoting and tracking the use of genetic markers to overturn wrongful convictions, reports that since 1989, nonmatching of genetic markers has exonerated more than 220 people, many of them convicted for rape crimes and some of them on death row.