That's a fair distinction. However, I think in this case there are very considerable indications of perjury and falsifying evidence on their part - certainly enough to invalidate everything they have thrown at Amanda and Raff (including the callunia charge against Amanda).
If they were to be charged with any of this, of course, then they would be entitled to presumption of innocence like any other accused.
Briars seems to "get" what's at stake here. If Curatolo is discredited for what many regard as obvious reasons, this almost surely means that Mignini was corrupt, in the sense of bringing evidence he almost certainly knew to be manufactured into court. That's why Briars has to change the subject to consider bloggers instead....
Same with Quintavalle. I mean, without him saying Knox bought anything, what, really, is the worth of Quintavalle's testimony? The implication perhaps is that they'd run out of bleach, or a mop, but mostly that Knox had lied about her own version of her movements.
If Quintavalle is bogus.... then again, my bias is that Mignini almost certainly brought an obvious whopper into court.
Then there are the motives Mignini considered. Statnic ritual? Sex-game gone wrong? Sour/ugly/revenge relations between Meredith and Knox? And then absolutely no motive at all?
At the very least the fictional "reasonable person" would conclude that Mignini never really did have a handle on how this crime happened (or why), and completely missed that the case was 100% complete by simply prosecuting Rudy alone.
There might be room for manoeuvring if Rudy is found guilty and AK and RS end up with a verdict which essentially says, "not proven". But the ISC seems to have perhaps taken care of that by wanting a better evaluation of "sex game gone wrong".
This requires the new prosecution to not just back up to the previously entertained motive which was abandoned, but the one before that which was abandoned even before!
Given my record for predictions, I'd say that the ISC was purposely trying to make Mignini look foolish. But given the record, I won't.
Did Mignini behave criminally? In my view he did if he condoned the manufacturing of evidence....