The “Grim Sleeper” serial killer was caught because California authorities found a partial DNA match with an individual in its database. That meant that the killer was probably related to the owner of that DNA, and indeed he was. We see this approach on the various “C.S.I” shows, but in real life using family DNA to identify a criminal is relatively rare, because only two states, Colorado and California, permit a  “familial search,” the use of DNA samples taken from convicted criminals to track down relatives who may themselves have committed a crime.

Why only two? The science is reliable, and a familial search can narrow the pool of suspects to the point where solving a crime becomes inevitable. Nevertheless, civil libertarians argue that the technique raises privacy concerns. Michael Risher, a lawyer with the American Civil Liberties Union of Northern California, told the New York Times there was the possibility of innocent people being harassed in the pursuit of a crime. “It has the potential to invade the privacy of a lot of people,” he said. Continue reading →