The trail of murders and assaults spanning California went unsolved for decades, until investigators turned to a tool more popular with genealogy hobbyists than law enforcement.

Investigators hoping to find the man who had become known as the “Golden State killer” obtained a genetic profile using crime scene DNA, and uploaded that information onto an open source database of publicly available genetic profiles. There was little expectation that the DNA would match directly with the killer. Investigators were instead conducting a familial DNA search in the hopes of finding a partial match that could lead to one of the killer’s relatives. Investigators were in luck, and within days, they located Joseph James DeAngelo, who was charged in April in connection with 12 murders in California during the 1970s and 1980s.