His alleged crime was to have shot dead a married man in cold blood and then raped his lover before shooting her repeatedly, paralysing her from the waist down.
The evidence presented at Hanratty's trial would almost certainly fail to secure a conviction in a court today. The case against him was at best flimsy, based largely on his identification by the crippled lover, who admitted she only saw him for a few seconds and failed to pick him out on the first police identity parade.
Yet despite almost 35 years of campaigning by Hanratty's family and supporters it is only now that the British justice system seems ready to admit it made a mistake.
Home Office officials are understood to have concluded that Hanratty was innocent. Michael Howard, the Home Secretary, is shortly expected to announce that he is to refer the case to the Court of Appeal, where the conviction is expected to be quashed.
But Hanratty's supporters will want to know why it has taken so long. Clearly, the wheels of justice often move very slowly. However, a less benign explanation could be that the exposure of one of the country's most infamous executions as a sham is a grave embarrassment and yet another plank in the argument against capital punishment. Indeed, the Scotland Yard detective who re-investigated the case is understood to have reversed his pro-hanging stance as a consequence.
The posthumous pardon of Hanratty would also raise the disturbing question: if Hanratty did not commit the murder, who did?
The killing shocked a nation not used to apparently random murders and acts of unspeakable brutality and cruelty.
The victims were Michael Gregsten, 36, a married man - whose regular infidelities were well known to his wife - and his mistress, Valerie Storie, 22. The couple had met at the government's Road Research Laboratory, near Slough, where he was a research scientist and she was his laboratory assistant.
The lovers used to rendezvous at a cornfield at Taplow, near Maidenhead in Berkshire. On the evening of 22 August 1961, they were together in Mr Gregsten's Morris Minor car when there was a sharp tap on the window. Gregsten wound it down to face a revolver. "This is a hold-up," announced the smartly dressed stranger. "I am a desperate man." He then climbed in and ordered Mr Gregsten to drive for about 60 miles through Slough and across the suburbs of north-west London before coming to a halt at a lay-by on the A6 near Bedford, known as Deadman's Hill.
At the end of the two-hour trip, he asked Mr Gregsten to pass him a duffle bag. As he did so, he was killed with two shots from the revolver. The murderer then raped Miss Storie on the back seat of the vehicle before shooting her repeatedly at close range, paralysing her for life. Afterwards, he fled in the car.
Throughout her six-hour ordeal Miss Storie only once saw the killer clearly - when his face was illuminated by the headlights of a passing car.
After Hanratty's arrest in Blackpool following his "identification" by Mr Gregsten's wife Janet, further investigations discovered two .38 cartridge cases from the gun used in the murder in room 24 of the Vienna Hotel in London, where the accused man had stayed under the false name of James Ryan.
In the first identity parade Miss Storie did not pick out Hanratty. At the second, she made each suspect repeat the sentence spoken by the killer: "Be quiet, will you, I am thinking." Like the murderer, Hanratty pronounced thinking "finking". After 20 minutes Hanratty was chosen by Miss Storie, who was confined to a wheelchair.
Documents released later showed that Miss Storie admitted:"I may not be able to pick him out. My memory of this man is fading". In addition, two earlier Identikit pictures she helped draw up did not match Hanratty.
Additional evidence against Hanratty was given by Charles France, a criminal, who committed suicide two weeks before the hanging. But it was the vital identification evidence given by Miss Storie that swayed the jury, who after nine-and-half hours delivered a guilty verdict.
On the morning of his execution at Bedford jail, Hanratty wrote to his family insisting that he was innocent and asking them to clear his name. His brother, Michael Hanratty, 58, said: "The day before Jimmy was hanged he said: `I'm dying tomorrow but I'm innocent. Clear my name.' This is what we need to be able to do."
The campaign has gone on ever since and during the past 35 years a wealth of evidence has emerged which supports the claim that an innocent man was wrongly executed.
One of the most implausible and incredible parts of the case against Hanratty is the acceptance that a town-dwelling bit-part criminal should stalk a couple to a cornfield in Berkshire to carry out a random killing. Moreover, there was not a shred of forensic evidence found in Mr Gregsten's vehicle to link Hanratty.
Hanratty also had a good alibi. At first he said he had been in Liverpool, but refused to name his friends. Extraordinarily, he changed his statement to say that he had stayed in a bed-and-breakfast house in Rhyl, North Wales - 250 miles from the scene of the crime. Again no witnesses were provided, but between 1966 and 1971 fourteen people came forward to support his story.
For many campaigners, including the journalist Paul Foot, author of the book Who killed Hanratty? The finger of guilt has long pointed at Peter Alphon, the man originally arrested for the murder, but later released.
Alphon, a former door-to-door salesman, had stayed at the Vienna Hotel, where the bullet cases were found, the night before Hanratty. Alphon, who pronounced "th" as "f" when excited, went missing on the night of the murder.
After the killing, Gregsten's Morris Minor was driven for several hours. Many witnesses said it was being driven erratically. Alphon could hardly drive, but Hanratty was experienced. Alphon also had a striking likeness to the Identikit picture produced immediately after the attack.
In addition, he was seen at the pub where the two lovers met on the night they were abducted. He has been reported as repeatedly admitting his guilt, claiming he was paid pounds 5,000 to break up the relationship between Gregsten and Storie.
Alphon, 66, made an alleged "confession" in Paris several years later saying that he was asked by someone close to Gregsten's family to frighten the couple. However, speaking to The Independent three days ago he denied that he had ever admitted to the killing and insisted that Hanratty was guilty. He said Hanratty had been hired by Mrs Gregsten to break up the relationship. "I don't have to prove my innocence," he added. Reports of his alleged confessions had been distorted.
Mrs Gregsten fiercely denied any involvement in a plot during a series of interviews with Paul Foot shortly before her death in January 1995. But she did admit that she was no longer convinced of Hanratty's guilt, pointing instead to Peter Alphon.
The growing doubts and pressure from campaigners and family - who have remained determined even since the death of James Hanratty Snr who protested defiantly outside the House of Commons - led to a fresh police inquiry into the case. Detective Superintendent Roger Matthews of Scotland Yard, who completed his report last year after an 18-month investigation, is understood to have concluded that Hanratty was wrongly hanged.
He believes that it is doubtful that an urban car thief would be in the countryside. Instead, it was probably a pre-meditated plan by someone hired to break up the relationship between Mr Gregsten and Miss Storie.
Geoffrey Bindman, the solicitor who has represented the Hanratty family for the past 25 years, said: "It's extremely difficult to persuade a government to reopen a case, although it has become less hard because of some noticeable miscarriages of justice such as the Birmingham Six. For many years it was practically unthinkable."
But the combined weight of evidence, backed by the police inquiry, appears to have been enough for the authorities to concede finally that a grave miscarriage of justice took place.Reuse content