Over a year ago, authorities in California finally tracked down an infamous rapist and murderer known as “the Golden State Killer.” The suspect was now in his 70s and the crimes had been committed in the mid-1970s and mid-1980s — but he had been identified through a combination of DNA and detective work.

Where did the DNA come from? Some of it came from his victims — but the DNA that allowed police to track him down came from his relatives. Those relatives had used for-profit genetic testing sites and public databases like 23andMe and Ancestry. Their genetic information allowed police to narrow down a list of suspects and zero in on one of their most-wanted criminals — long after he probably expected to get away with his crimes for good.

Since then, similar investigations have been used more than 50 times to identify criminal suspects. Authorities speculate that the popularity of such genetic databases will continue to grow and eventually give officials the ability to solve thousands — or tens of thousands — of previously unsolved violent crimes. In many cases, the suspects that have been identified through these investigative methods were never even on the radar during investigations.

It’s important to understand that this is all being done legally — with the full cooperation of the companies that are allowing their databases to be used. For example, FamilyTreeDNA specifically altered its terms of service agreement to permit law enforcement agencies to upload genetic samples for familial matching. While customers can “opt out,” only 1% do so.

Not everyone is a fan of the whole thing. Some lawmakers have even introduced bills to stop police from using genealogy tests to hunt criminals down. Others call it a vast invasion of privacy. For now, however, anyone who ever committed a crime in their youth — no matter how long ago — may have reason to be concerned if they left behind DNA.

If you find yourself facing felony charges from a long-ago event, make sure that you have an experienced defense attorney protecting your interests.