There's no Silver Bullet.
I don't know the standard. I think one way the Feds can get involved is to protect someone's civil rights.
I would think the standard in general wouldn't be too high, because using corruption as an example - no ruling or finding locally would trigger them because a corrupt system by definition wouldn't trigger or dial for help. Maybe the Defense lawyers have to convince the Feds that the local authorities are unethical or not following the law.
Tucker Carlson is going to be discussing the Duke case soon
Tucker Carlson MSNBC, if you care to watch
I'd better stop asking questions--I am going to have nightmares.
I agree--NO silver bullet, ace in the hole, magic carpet ride, whatever.