Grim Sleeper Awakens Attention to Familial Searching of DNA Databases

Last week, the Los Angeles Police Department announced that it had captured a man suspected of being the “Grim Sleeper”: a serial killer linked with at least 10 murders over 25 years.1 The case marks the first time in the United States that a DNA search technique known as familial searching has led to an arrest in a homicide case.

As we’ve previously discussed, a partial match between two DNA profiles may indicate that the donors of the corresponding samples may be related. In familial searching, a database is searched for the purpose of identifying partial, rather than exact, matches against the sample of unknown origin. Those partial matches are then used as investigatory leads.

Though familial searching has been used with some success in other countries, few states openly endorse its practice. Those states that permit the use of partial matches at all generally prohibit the intentional search for those matches, requiring instead that they be discovered inadvertently. California began using familial searching in 2008 in a first attempt to identify the Grim Sleeper. At the time, the failure to produce a suspect was seen as a strike against the technique: if familial searching could implicate privacy concerns and subject innocent individuals to excessive genetic surveillance, it certainly could not be justified without being able to point to positive results.2 Since then, one DNA profile of particular interest was added to California’s database: that belonging to the son of the man now identified as the Grim Sleeper.

While these concerns—which focus on the broad impact of sustained, widespread familial searching—cannot be overcome simply by reference to discrete cases, the procedure followed by the DNA laboratory that conducted the tests in this case seems to have at least helped to assuage the critics. As discussed by Maura Dolan in the Los Angeles Times, the ACLU of Southern California endorsed the procedure utilized by the investigative team, which included control of the investigation by a “familial search committee.” For instance, unanimous approval of the committee was required both before the name of the partial match donor was released to the Department of Justice and before the name of the suspect and the supporting DNA findings were released to the Los Angeles Police Department.

The capture of a high-profile serial killer will likely spur public opinion in support of familial searching. The fact that the ACLU (which is the motivating force in a lawsuit challenging another of California’s controversial DNA practices, the collection of DNA samples from individuals upon arrest) has endorsed the practice used by the state in achieving the arrest is likely to garner additional attention. We’ll keep you updated as more jurisdictions explore the possibility of implementing formal policies concerning familial searching.

[Update 7/15: The ACLU attorney quoted in Dolan’s LA Times article has contacted the GLR to clarify that they do not “endorse” familial searching. Instead, the ACLU believes that the procedures used in familial search investigations deserve statutory protection and additional oversight, which they argue for in a post on their own blog.]


1 He has since been charged with 10 counts of murder, with the arraignment scheduled for August 9. At this point, the presumption of innocence must be respected. The material contained in this post is intended for discussion purposes only and should not be construed as an opinion on the guilt or innocence of the individual charged.

2 As detailed in an earlier post, one common concern voiced by critics of familial searching is that because minorities are disproportionately represented in DNA databases they would in turn be disproportionately implicated by the results of familial searching.