On 4 April 1962, James Hanratty was led from the condemned cell in Bedford Prison to the gallows. On the way he protested his innocence, as he had done every day since he had been convicted of murder. At 8am, the noose was fitted round Hanratty's neck and he was hanged, launching one of the longest and most bitter appeal campaigns in the history of British justice. Hanratty's supporters believe that he was wrongfully convicted, the victim of dubious police evidence. The police maintain Hanratty was a vicious killer - and say they now have DNA evidence to prove it. After years of doubt, it appears that modern science holds the key to a 40 year old case. It all began when Michael Gregsten drove to the countryside with his lover, Valerie Storie. They had just parked in a quiet lay-by when a gunman got in the back of their car and demanded money. Several hours later Gregsten was dead and Storie had been raped and, with several bullets inside her, left for dead on the side of the A6 road. Amazingly, she survived to tell the tale. The nation was horrified by the savagery of the crime, and a massive manhunt was launched. Police began to close in on a small-time crook, 25 year old James Hanratty. Valerie Storie identified him as the killer, as did two other eye witnesses, who said they saw Hanratty driving Gregsten's car shortly before it was abandoned. Hanratty, a convicted thief, was unable to provide a credible alibi for what he was doing at the time of the murder, and in court, came across as arrogant, devious and unreliable. After a six week trial, and largely on the basis of this crucial eye witness evidence, Hanratty was found guilty and sentenced to death. As time went on, Hanratty campaigners became more and more convinced that the case against him was flawed. They claim that police withheld vital evidence from the defence, that Valerie Storie's identification of Hanratty was dubious, and the other eye witnesses may not even have seen Hanratty at all. The case against Hanratty began to look sufficiently weak that an appeal was begun, nearly 40 years after Hanratty was hanged. As part of the re-examination of the case, painstaking forensic analysis of the original police notebooks suggests that the police may even have altered the records of their interviews with Hanratty. So for Hanratty campaigners, on the evidence as presented in court in 1962, Hanratty should never have been hanged. Horizon has unique access to footage that covers a bizarre twist to this strange story. In 2001 the police exhumed Hanratty's body and took DNA samples, for comparison with crime-scene evidence still stored in police files. Using advanced techniques in DNA analysis which can analyse tiny fragments of DNA - even those from decaying, 40 year old corpses - the scientists made a conclusive match. It seemed that for all the campaign, Hanratty may well have been guilty after all. But with the judgement of the original trial possibly flawed by the suggestion of undisclosed evidence and police interference, the Court of Appeal faced a highly difficult decision. It had to decide whether the original evidence leading to Hanratty's conviction was so flawed that the guilty verdict should be overturned; or whether the case against him, including the new DNA evidence, was so compelling that the guilty verdict should remain. The A6 Murder looks at the evidence that led to two weeks of deliberation for the judges, and discusses where both sides go from here.