Yesterday’s arrest of a suspect in the long-running “Grim Sleeper” killings was made possible by familial DNA searching—in a nutshell, the suspect’s genetic material wasn’t in California’s database, but a family member’s was. A paper from earlier this year explains how the Golden State decides when such a search is enough to warrant further investigation:
In April 2008, the California Department of Justice relaxed its policies to allow for familial DNA searches and the reporting of results to authorities for further investigation. The policy shift makes California the national leader in familial DNA searching. Unlike other states, California vigorously pursues familial searching as a matter of policy rather than happenstance. California’s policy requires a sharing of at least 15 alleles, additional DNA testing, and a prosecution committee review before the pivot’s name will be released to authorities. But the policy lacks any similar safeguards for the relatives of the pivot who may be implicated by the results of a familial search. California Attorney General Jerry Brown stated that the new policy was warranted because of the rise in violent crime in the state.
Expect a ton of debate on this investigatory technique in the coming days. We anticipate that the positive press stemming from the alleged Grim Sleeper’s arrest will pressure other states to follow California’s lead. And that will inevitably lead to a lot more cases in which innocents are compelled to give up DNA, because their familial connections automatically bring them under suspicion.