Federal and local law enforcement have used public genealogy databases for more than two years to solve cold cases, including the landmark capture of the suspected Golden State Killer, but the cooperation with Family Tree DNA and the FBI marks the first time a private firm has agreed to voluntarily allow law enforcement access to its database.

While the FBI does not have the ability to freely browse genetic profiles in the library, the move is sure to raise privacy concerns about law enforcement gaining the ability to look for DNA matches, or more likely, relatives linked by uploaded user data.

For law enforcement officials, the access could be the key to unlocking murders and rapes that have gone cold for years, opening up what many argue is the greatest investigative tactic since the advent of DNA identification. For privacy advocates, the FBI’s new ability to match the genetic profiles from a private company could set a dangerous precedent in a world where DNA test kits have become as common as a Christmas stocking stuffer.