One such case is that of Martin O'Halloran, who was given life for the murder of a gay hairdresser, Thomas Walker, in 1976. O'Halloran's conviction, secured just two months after that of the Birmingham Six, will once again turn the spotlight on the police procedure.
The case has echoes of Stefan Kisko, the man with a mental age of 12 who was wrongly convicted of raping and murdering a young girl. O'Halloran, 49, has a low IQ and was illiterate when he was arrested. He has spent almost all his adult life in prison. The BBC's Rough Justice programme, broadcast tomorrow, has found letters from the co-accused (O'Halloran's best friend) confessing to the murder and has reinterviewed witnesses whose original statements supported O'Halloran's version of events. Called The Price of Friendship, the programme charts extraordinary events in which O'Halloran's sister, girlfriend and, most damagingly, best friend testified against him.
The friend, Arthur Langford, relied on O'Halloran's poor memory and low IQ to convince him that the two were with each other in London at the time of the murder. O'Halloran confirmed this to the police, although he had already said that he had been meeting his girlfriend in London. Langford, who has since died, then changed his story to accuse O'Halloran of the murder. Like Kisko, also accused of a sex crime, O'Halloran's low intelligence and illiteracy were not taken into account during his prosecution, but were used against him. On several occasions O'Halloran broke down while being questioned by the police. Langford told police that O'Halloran had attacked Thomas after all three had been drinking in a well-known gay pub. This supported the police's belief that Thomas had been the victim of a "queer rolling". O'Halloran's sister told the court that Langford and her brother came to her house in Birmingham in the early hours of the morning and confessed to the crime.
When the judge asked him why his sister had come to court to give evidence against him, O'Halloran said it was because she was in love with Langford and she thought O'Halloran had "taken him away from her". His alibi was further shattered when his then girlfriend told police that she had not met him that evening, as he had claimed. The evidence appeared overwhelming, and the jury took just three hours to find him guilty of murder.
However, the Rough Justice team has spoken to Langford's daughter, Maggie Phillips, who says that her father went to his grave protesting O'Halloran's innocence. In a letter written to O'Halloran, he said: "I did this killing on my own." Langford repeated this to O'Halloran's lawyers.
Maggie Phillips concludes: "He was adamant that he'd done it. And he would not say that and stick to it all this time if it weren't true. My dad is dead now, and Mark [Martin O'Halloran was known to her as Mark] is still in prison for something that he didn't do."
Rough Justice has reinterviewed some of the witnesses, including O'Halloran's girlfriend, Patricia Riorden, who said that she gave six statements to the police. The first of these confirmed O'Halloran's alibi that he had been in London with her. Moreover, the programme's researchers have also spoken to Patricia's father, who also backed up O'Halloran's version of events.
Jeremy Dein, a barrister, says: "The procedures that were followed were laughable. Today, the evidence of witnesses, who identified O'Halloran by photographs, would not see the light of day. The witnesses expressed themselves in vague terms. There was no positive identification."
The case demonstrates how much has changed since the Seventies, when criminal justice procedure was uncodified. Before the birth of the Police and Criminal Evidence Act 1984 and the Crown Prosecution Service, the police decided what evidence to disclose. In another echo of the Kisko case, police evidence that would have supported O'Halloran's alibi was not given sufficient weight at the time of his trial. In the Kisko case it was a woman, his mother, who brought the case to the attention of the authorities. For O'Halloran the key person in his fight back has been his wife, Margaret, a Quaker who married Martin in1995 after meeting him during a prison visit when she stood in for a friend.
Like Kisko's mother, who fought tirelessly to overturn her son's conviction, Margaret O'Halloran has spent the last few years digging up evidence that she hopes will prove his innocence. This evidence, including Langford's confession letters, has been sent to the Criminal Cases Review Commission. But because the Commission has a two-year backlog before it can even consider a case for review, O'Halloran's wife and other supporters fear he may die before the courts can clear his name. He has already suffered two strokes, and, although the Commission does have a fast-track procedure for exceptional cases, it could be another three-and-a-half years before his situation is reassessed by the Court of Appeal.
Although the Criminal Cases Review Commission celebrated its second anniversary earlier this year, and has been given increased funding, it still receives more new cases each week than it finishes reviewing. The Home Affairs Select Committee said in March that delays were unacceptable and recommended that the Government and the commission make it a priority to speed up the handling of cases. In December, Sir Frederick Crawford, the commission's chairman, admitted it would take many years to clear the backlog because a lack of money meant that there were only 25 case workers instead of the 60 needed. Lawyers have suggested that the commission's time would be best used concentrating on cases in which the accused is still alive rather than reviewing cases where the only remedy is a posthumous one, such as those of James Hanratty and Derek Bentley. Stefan Kisko was eventually released, but died in 1992 from what many believe was the trauma of being imprisoned for a crime he had not committed.
Margaret O'Halloran says: "Martin could go at any time, and I hope his name is cleared before he dies. I hope he can live some time out here in the open, where he should have been for the past 24 years."
`Rough Justice: The Price of Friendship' will be shown on BBC1 tomorrow (2 June) at 10.30pm