An expert witness for the defense? That's supposed to settle things?
(1) Given that you're the one who goes around saying that the opinions of (non-expert!) judges and jurors should settle things, and thus apparently places a high value on the opinions of socially recognized "authorities", it's utterly hypocritical of you to now suggest that we should believe Giancarlo Massei's interpretation of pathological data over that of Carlo Torre. Here's
Torre's CV, for whatever it's worth.
(2) It should be obvious that whether things are "settled" or not depends on what the witness actually says. Torre was unequivocal:
io non ho alcun elemento che mi suggerisca anche solo
remotamente l’intervento di più di una persona … Gliel’ho detto non
vedo tracce di altre persone (AK's appeal, p. 102)
I don't have any evidence that even remotely suggests to me the intervention of more than one person....I've told you, I don't see indications of other people.
(3) You may worry that Torre is being paid by the defense, and may have an incentive to come to a certain conclusion. But if you actually think about this for a few seconds, instead of just automatically categorizing it under some standard narrative of "one side says this, the other side says that", you'll realize that someone of Torre's prestige level is highly unlikely to risk his professional credibility among his colleagues by making a statement as categorical as the above in a situation where there
was in fact evidence that would convince a neutral pathologist of multiple attackers. And if you think that expert witnesses will just automatically say whatever would be good for their side, even if it's manifestly false, then why bother having them testify at all?
(4) If you worry that Torre's testimony was somehow the result of a filtering process by the defense, wherein they interviewed experts until they could find someone to say what they wanted,
here (see 8:08) is a video explaining that Torre got involved on his own initiative, after being told about the case by a journalist.
ETA: I'd like to add by the way that Torre's testimony
alone -- the inability of the prosecution to convince a leading pathologist that there was more than one attacker -- constitutes reasonable doubt and grounds for acquittal, which just shows how far people are from intuitively understanding what "beyond reasonable doubt" actually means.