John McLay was 17 when he was sentenced to life for stabbing Stephen McDermott, 27, outside his home in Glasgow during a night of violence in February, 1992.
Now, 21 years later, he aims to prove he was the victim of a miscarriage of justice. Seven affidavits at the centre of his case, including one from a prison officer, say his co-accused Stephen Harkins had bragged about being the real murderer before his death.
Now 37, with a 21-year-old son, McLay says he has tried to kill himself three times as a result of "the torment of what happened" and added: "I will fight my case till my dying breath and will leave no stone unturned. I am prepared to take a lie detector test if necessary."
McLay and his co-accused blamed each other for the murder, with both said to have been "full of jellies" – a reference to the drug temazepam – at the time. The trial judge, Lord Prosser, told the jury during the trial that there appeared to be substantial evidence against Harkins, who had already used his knife on another man that night. Only one person had stabbed Mr McDermott.
But there was also blood on a distinctive jacket said to have been worn by McLay.
The jury found the murder charge against Harkins – then 22 – not proven, while McLay was found guilty.
Subsequent sworn statements that Harkins had admitted sole responsibility for the murder before and after the trial were deemed "hearsay evidence", and McLay was not allowed to use them in an appeal that subsequently failed.
However, in December, 1997, then Scottish Secretary Donald Dewar referred the case to the Court of Appeal in a landmark ruling that resulted in the statements being considered. New laws allow evidence that comes to light after a conviction to be admitted as grounds for appeal.
That evidence included a statement from William Blake, a prison officer in Greenock Prison, who said Harkins told him McLay was serving life for a murder he had not committed.
Court papers say: "Blake had not been interested because it was raining and they were trying to get through the grill gate, but Harkins went on and said, 'I know who did it – I did it'."
It did not occur to him to tell senior officers immediately and he refused to give an affidavit at first as he feared harm would come to him, court papers show.
He eventually made a statement after Harkins died in January 1999.
Other evidence was provided by two convicted murderers and a robber serving eight years.
But in April, 2000, Lord Coulsfield dismissed the appeal, and questioned the admissions, saying Harkins was regarded, by other prisoners and by prison officers, as "boastful, a nuisance and a person who was in the habit of indulging in bravado".
McLay from Knightswood, Glasgow, who has since adopted his father's name of McIntosh, said: "It hurts me that the Court of Appeal had the chance to put things right but chose to brush me off by simply saying Harkins was just boasting.
"It was just the easy way out for the court."
While in prison he says he wrote to the murder victim's parents to apologise for being involved "in such a horrific case" but claimed he did not kill their son. There was no reply.
A year after Lord Coulsfield's ruling, McLay was released on "interim liberation". He said: "I have this case on my mind every waking hour. It's like a dull headache that never goes away."