My view is that anything presently regarding Mignini from an innocence side of the fence is "conspiracy theory", rather than hard and fast evidence. My bias, though, is that it is a conspiracy theory with some merit.
I have two words that perhaps can decide it one way or another.
Wladimiro De Nunzio.
Ok, ok, that's three words. Conspiracy theorists on both sides disagree on his role, but both sides agree that president of the Perugia Court of Appeal, Wladimiro De Nunzio, has something to do with this in his appointment of Hellmann to contact the 1st Second grade appeal's trial.
I suppose there's a third alternative - that BOTH sides in their various conspiracy theories are nuts and bonkers. Maybe De Nunzio just made the appointment because Hellmann was the next judge available....
But guilters say that De Nunzio purposely manipulated the appointment of the Appeal's judge to embarrass Mignini, and innocentisti say that De Nunzio wisely appointed Hellmann to undo the mess Mignini/Massei created.
Your mileage will vary.
Me, I want to know more about De Nunzio. However, after savaging him on line, Machiavelli won't talk about him any more.