Catching criminals through their relatives' DNA

Harvard University researchers say recent cases demonstrate the potential of using the DNA of relatives to catch guilty kin. "Close relatives have particularly similar DNA profiles due to shared ancestry," notes David Lazer, an associate professor of public policy at the Kennedy School of Government. "[T]his could be exploited in criminal investigations."

Lazer, along with colleagues Frederick Bieber, a pathologist at Harvard Medical School, and Charles Brenner, a mathematician at the University of California, Berkeley, designed computer experiments to demonstrate their point. The team started with a DNA sample from a crime scene that failed to be an exact match to any profile in a large, up-to-date database. Their computer program compared this sample to the DNA profiles of 50,000 offenders in what they call "a typical-sized state database." Offenders with the closest matches would, in an actual forensic investigation, be singled out as possible relatives of the suspect.

From this simulation, they concluded that a parent or child of the suspect would be identified as the first candidate more than half (62 percent) of the time. Looking at the top 100 candidates, they raised their success rate for finding the best candidate to 99 percent. Further analysis showed they could also identify brothers and sisters of the suspect whose DNA they had, albeit at a slightly lower success rate.

Their report was published in the online version of the May 12, 2006 issue of the journal Science.