Of course the list is long on the mishandling of evidence.
The absence of any "missing evidence" means nothing when you have a severely mishandled crime scene, for example, computer experts who ruin several hard drives and <enter long list of other mishandled items here...semen stain...stomache contents>
I doubt they looked very hard for anyone else.
Personally, I think the prosecution and early helpers were fooled by Rudy Guede. What if all of this is ongoing because Mignini is nothing but a fool, and the system blindly supported him.
Then the PGP believe in the Mignini Religion, because they trust that the polizia and forensic team must be correct because they have specialists like Edgardo Giobbi, Computer Experts, and Stefonani.
A castle full of fools, maybe? Rudy Guede fooled them all and will be out laughing soon enough at the Clown Cops who weren't smart enough to run the investigation or count tennis shoeprint circles.
In my opinion, there's an extremely simple and entirely plausible reason for the whole debacle. It's as follows: Mignini and the state police were under massive pressure to be speedy and competent in investigating this murder - and, probably even more importantly, to be
seen to be speedy and competent.
And that (in my view) was due to two major reasons: firstly, this was by some distance the most high-profile "whodunnit" serious crime that the Perugia authorities had faced in many years* (maybe decades) - it had an international aspect, a "beautiful young exchange student brutally killer in her own home" aspect; the international media were pouring into Perugia in droves as a result, and they were all looking directly at Mignini and the Perugia police for answers. And secondly, I don't think we should underestimate the fact that the authorities had totally botched another not-dissimilar (but much lower-profile) murder almost exactly a year previously, and had been roundly criticised for their incompetence and mismanagement.
I think all of the above (and the asterisk point below) led the authorities to rush to judgement. They quite clearly (in my view) developed severe tunnel vision and confirmation bias within even hours of the discovery of the body. By the 5th November, I believe that the tunnel vision and confirmation bias - aided and abetted by some undoubtedly unorthodox behaviour from Knox - had manifested themselves in what the authorities clearly (and vocally) considered to be a cast-iron theory which "solved" the murder. They coerced Knox into "confirming" their theory. They all slapped themselves heartily on the back for a "job well done", and basked in the superficial adulation of the world's media and the Perugia public.
After all that, I think it was nothing more complicated than a combination of personal hubris, authority groupthink, and an institutional circling-of-the-wagons once large holes began to appear in the "theory". I think they were all more than reluctant to admit that they'd got it wrong, for fear of being once more labelled incompetent and unreliable. And from then on..... QED.
* Add to this the complicating factor that it was the State Police who - by happenstance - were the body leading the investigation, rather than the Carabinieri, who were the normal "go to" police force for serious crimes such as this one, and who were undoubtedly much more used to - and equipped for - investigations of this nature. I believe that, as a result, the State Police very likely felt they had something to prove in the way they handled the Kercher investigation, and that this added further to the refusal to admit (or even understand) that their original (Nov 6th) theory of the crime was totally wrong.
