"President Trump declared at a rally in West Virginia that ‘the Russia story is a total fabrication. It’s just an excuse for the greatest loss in the history of American politics.’ Trump’s comments, which were meant to denigrate and perhaps thwart the Mueller probe, were undermined by the fact that the grand jury has been at work for several weeks in the District of Columbia. Grand juries don’t investigate hoaxes, and there are rules against using them for anything resembling a political witch hunt. As several former federal prosecutors told me, the grand jury is significant because it means that Mueller is in the midst of a ‘predicated’ criminal investigation. That is, he has reached the point where he has evidence of criminal conduct. ‘It can’t be used for a fishing expedition,’ Matt Olsen, a former federal prosecutor, said."