Sisko got his fingerprints scanned to get his ID badge, which means everyone in a Sanctuary has their fingerprints on file. The real Gabriel Bell was killed in full view of the police, but his death was never logged because he didn't have his ID card on him. Later, Bell is considered dead because his ID card was found on a different body, even though that body doesn't match his record. The government apparently cares so little about the people in Sanctuaries that they don't bother to use their fingerprints on file to ID or verify the identity of bodies.
