One issue I see in some posts here is that there is a lack of skepticism about the claims of police and prosecutors, and of course Mignini and the Italian police specifically.
There seems to be a reluctance to accept that official misconduct is a real phenomenon that occurs in some cases, as a deliberate effort by the police and/or prosecutor, whatever the motivation may be.
To show evidence that such official misconduct occurs, here is an excerpt from a recent article dealing with the case of prosecutor Charles Sebasta in Texas, who was disbarred for official misconduct which resulted in the wrongful conviction of Anthony Graves for murder.
Prosecutor who sent innocent man to death row is disbarred
Updated 9:03 am, Tuesday, February 9, 2016
"In a ruling issued when [Charles] Sebesta was originally disbarred, the disciplinary panel found that he failed to provide several items of exculpatory evidence to the defense during [Anthony] Graves' trial, presented false testimony to the jury, made a false statement of material fact to the trial judge and engaged in conduct involving dishonesty, fraud, deceit or misrepresentation."
Source:
http://www.chron.com/news/article/Disbarment-of-Texas-prosecutor-of-ex-death-row-6817491.php