Re: Proof of ownership?
I'm not sure that this is an issue here. If the FBI submits the DNA of an unidentified body, so as to identify it and contact relatives, it's acting legitimately on behalf of the interests of that person. If it submits DNA from a crime scene, the criminal has forefeited any right to privacy by his act.
The issue is that the people in the database are having their privacy violated, by having their DNA matched under circumstances different from what they expected - by long-lost relatives looking for them. And so the fact that the FBI is getting the same information as a regular customer is relevant even if not decisive.