If you're concerned about misuse of a DNA database, you should be arguing that the DNA database shouldn't exist at all, not that we should have a bunch of silly rules about how it can or can't be used. Bush's cronies, or the equivalent, are ignoring the rules already; they're hardly going to care about one more rule to ignore.

In the specific case that a crime has been committed, and the police have a DNA sample that they are 100% certain belongs to someone at the crime scene? I think they should use whatever data they can get their hands on, and I'm perfectly fine with tracking people via their relatives as long as it doesn't cause trouble from false positives.

I sort of agree with you that maybe the government shouldn't have a DNA database. But your poisoned-fruit rule would hamper the "good guys" without inconveniencing the abusers at all.