Factual error: When the convictions are overturned, the defendants' solicitor, Gareth Pearce (played by Emma Thompson) is shown arguing their case in court. In England solicitors cannot appear in the higher courts, and in fact a barrister presented the case. However, the film is 'dramatically correct' because it was Gareth Pearce who got them freed, and the barrister in question is far too full of herself without having the honour of being portrayed by Emma T.
Other mistake: The inmates are watching "The Godfather"; specifically, the scene towards the end in which Don Corleone is speaking to Michael in the garden. Just before the inmates light the guard on fire, the audio jumps backwards: after we hear Don Corleone say "Whoever comes to you with this Barzini business...", the next line we hear is "I knew that Santino was gonna have to go through all this...", which is from earlier in the same scene. We then see the film and see Don Corleone's lips forming the line that follows the Barzini line, while the audio continues with the incorrect, earlier line. (01:35:15)