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How to Nab a Serial Killer

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For more than two decades, the Grim Sleeper had stalked the streets of Los Angeles, brutally murdering at least eleven people. He left his DNA—but without a match in convicted-offender databases, police were stymied. Then, in July 2010, DNA from a discarded pizza crust led to the arrest of a suspect. A new tool, known as familial DNA searching, had identified him through a partial match to his son, whose DNA profile was in California’s convicted-offender database. Familial searches of DNA databases—and, in some cases, lunch remnants—hold great promise for unlocking even the most enigmatic crimes.

Explore family ties.

I’ve worked with several teams to identify victims of mass disasters and war—including those who died in the September 11 terrorist attacks and in Hurricane Katrina—using DNA from their relatives. These experiences triggered a eureka moment for me: Why not use these powerful kinship tools to search for possible suspects in criminal investigations?

Build a genetic library.

Familial searching methods have been used to solve crimes in England, where DNA samples are taken upon arrest for most offenses and the profiles saved in a large, searchable database. In 2006 I coauthored a Science paper illustrating the power of kinship analysis for indirectly identifying criminal suspects. We estimated that this approach could increase the “cold-hit” rate—the chance of matching a crime-scene sample with a suspect—by 40 percent. In 2008, California became the first state to approve an official policy for familial DNA searching; two years later the Grim Sleeper investigation became the first California case to employ this method.

Engage in the debate.

Despite successes here and abroad, familial DNA searching isn’t without controversy. Critics argue that the process invades the privacy of criminals’ relatives. Yet most of the work happens behind the scenes, with relatives rarely contacted. Moreover, familial DNA—a valuable tool for identifying missing persons and determining paternity—is increasingly used to exonerate the innocent. Used judiciously, this technique can help shed light on some of human nature’s darker mysteries.

Frederick R. Bieber, PhD, is an HMS associate professor of pathology at Brigham and Women’s Hospital.

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