More than half a century after his conviction, a County Antrim man who was tortured into making false admissions about explosives is to have those convictions quashed.

The Court of Appeal in Belfast has ruled that the case against Laurence O’Neill was fundamentally undermined by the non-disclosure of medical evidence showing he had sustained injuries while in custody.

Senior judges concluded that this failure fatally weakened the reliability of the confession evidence relied upon at his trial.

Describing the original proceedings as “unconscionable”, the Chief Justice, Dame Siobhan Keegan, said the court could not be satisfied that the convictions were safe.

Mr O’Neill (pictured), now aged 82, said the decision finally cleared his name after decades of campaigning. Speaking outside court, he said: “I have waited 54 years for this day, and I feel elated.”

He went on to describe the conditions of his interrogation, saying: “Torture wouldn’t describe what happened to me, I was interrogated for four and a half days around the clock with no food, no sleep and no toilet.”

Mr O’Neill was convicted in 1972 of possessing ammunition with intent and possessing explosives with intent to endanger life. He was sentenced to 15 years in prison and served eight years.

The charges arose from an incident in November 1971. Mr O’Neill was sitting in a car outside an address in Belfast when he was approached by two members of the Scots Guards. He said at the time that he was waiting for someone inside the property, but they denied knowing him.

A search of the vehicle supposedly uncovered 700 rounds of ammunition hidden in a concealed compartment on the driver’s side. The following day, a quantity of arms was discovered at his family’s farm.

After his arrest, Mr O’Neill was taken to Palace Barracks in Holywood, County Down. He was interrogated and assaulted on six occasions by Special Branch officers without a lawyer present. He was later medically examined and several injuries were recorded, according to a body that investigates potential miscarriages of justice.

At trial, an RUC police detective falsely claimed Mr O’Neill had admitted responsibility for the ammunition but had refused to sign a written statement.

Decades later, in 2016, documents connected to a civil action in the case were uncovered at the Public Records Office in London by the Pat Finucane Centre.

Following that discovery, Mr O’Neill’s legal team asked the Criminal Cases Review Commission to review the safety of his convictions. The CCRC referred the case back to the Court of Appeal, citing concerns about the use of torture or inhuman and degrading treatment during his interrogation.

Referring to “executive misconduct”, the inadmissibility of confession evidence and the lack of sufficient supporting evidence, the commission said there was a real possibility the convictions would not be upheld.

During the hearing this week, the court was told that the findings of a British Army doctor who examined Mr O’Neill while he was detained at Palace Barracks had been withheld from the original trial. His barrister, Brian Fee KC, said the medical report detailed significant injuries consistent with the abuse his client said he had suffered.

“This has been a long and winding road for the appellant, allow him to live out what’s left of his life free from the stain of convictions which should not have been imposed upon him,” Mr Fee told the court.

The appeal was not opposed by the Crown Prosecution Service.

Outside court, Mr O’Neill spoke of the impact the injuries had on him at the time, recalling that his own father failed to recognise him when he saw him at the RUC barracks.

Reflecting on the wider context of the period, Mr O’Neill said: “I was born and reared in a sectarian state, the police force that operated then did what they were instructed to do, and that was to torture their subjects.”

His lawyer, Patricia Coyle of Harte Coyle Collins, said he had endured “horrendous” treatment while in custody. “There were physical beatings and firearms with blanks in them were discharged against his ears,” she said.

She added that his experience was not unique, saying: “He was within a cohort of victims from August 1971 who were essentially used as guinea pigs by the state.”

Ms Coyle said the ruling marked a decisive moment.

“Those who subjected my client to this conduct operated in the dark, but that apparatus of denial has been demolished today,” she said.

Paul O’Connor of the Pat Finucane Centre said the documents uncovered in London showed how widely known Mr O’Neill’s treatment had been. “The striking thing about the documents in Kew is how many people knew what had happened to Laurence,” he said.

“His treatment has been described as torture, and that is what people need to hear.”