Yep, it is the FBI's job, but it's also the job of two separate attys, neither of which thought there was a thing to it. It was the easiest, most foolproof defense possible for either McV. or N, to say there were others involved and they could avoid the chair (or life) if they named names. Yet no one did. Hmmmmm. Very peculiar. Guess the defense attys are "in on it too," so now we have the prosecution, the defense, the FBI, all the jurors---that would be FOUR juries---all of whom were part of this giant coverup.
Oh, and McV and Nichols themselves, yep they were part of it too. Puh-lease.