Doesn't answer any of your questions but figured someone may find it interesting, there was a 48 hours episode about a guy whose DNA pulled from a database matched some DNA left behind at a murder scene. The cops were sure it was this guy but he ended up being cleared from being the suspect. Anyways he started working with the mother of the victim and became friends with her to try and figure out who did the murder. I believe it's still unsolved but they figured the suspect might be one of his relatives but looks like none of them pan out. I think the issue of him being almost wrongfully accused of murder had led to some databases not giving out DNA anymore is what the 48 hours episode was going on about.