Investigators are analyzing DNA and using basic genealogy to find relatives of potential suspects in the hope that “familial searches” will lead them to the killer. Familial searches led to the arrest of Joseph James DeAngelo in California’s Golden State Killer probe in April. Investigators have used it to make breakthroughs in other unsolved murder cases, including four in Washington state, Pennsylvania, Texas and North Carolina, McClatchy Newspapers reports. As such searches proliferate, they are raising concerns about police engagement in “DNA dragnets” and “genetic stop and frisk” techniques. Investigators may soon have the ability to track down nearly anyone, even people who never submitted their genetic material for analysis. “If you are a privacy zealot, this is super alarming. It means you don’t have any privacy,” said Malia Fullerton, a bioethics specialist at the University of Washington. “On the other hand, if you have no problem with police using your family information to solve these cold cases, you might see this as a good thing.”

Law enforcement is aided by open-access DNA databases that did not exist a decade ago. Florida-based GEDmatch, founded in 2010, allows genealogy enthusiasts to share their DNA profiles, created from commercial services such as Ancestry and 23andMe. The site has rapidly grown to more than 920,000 profiles. It’s proved a gold mine for law enforcement. In the Golden State Killer probe, before identifying DeAngelo, investigators reportedly assembled 25 family trees, possibly involving 1,000 people. Fullerton and collaborator Rori Rohlfs argue that the case shows how innocent bystanders can be ensnared through familial searches. “These details, many of which only came to light after intense press coverage, raise a host of concerns about the methods employed (by police) and the degree to which they exposed otherwise innocent individuals to harms associated with unjustified privacy intrusions,” they wrote in Leapsmag, an online magazine.