The Irish state has formally apologised to the family of Brian Stack, a senior prison officer murdered by the IRA, for serious failings in the investigations into his killing.
Stack, a father of three and chief prison officer at the high-security Portlaoise Prison, was shot in the back of the neck as he crossed a street in Dublin after leaving a boxing match in 1983. He was left paralysed and died 18 months later, aged 49.
Three separate Garda investigations were conducted into his death, but no one was ever brought to justice for the killing.
Taoiseach Micheál Martin delivered the formal apology on behalf of the state during a sitting of the Dáil on Wednesday. Stack's wife Sheila and their sons Austin, Kieran and Oliver were present in the chamber.
Prior to the Dáil proceedings, the Stack family held a private meeting at government buildings with the Taoiseach and Minister for Justice Jim O'Callaghan.
In 2007, the Garda Commissioner directed a review of the case by the Garda Serious Crime Review Team. The review found serious failings and shortcomings in the management of the earlier Garda investigation, and resulted in over 200 recommendations.
Among the failures listed by Martin in the Dáil were: a failure to preserve a map of the crime scene; a failure to retain a motorbike helmet found near the scene and linked to the crime; and a failure to maintain custody of material exhibits, including fingerprints, samples and debris gathered during the investigation.
The Taoiseach also cited a failure to document key aspects of the original investigation, including whether colleagues and prisoners at Portlaoise Prison were interviewed, and a failure to interview the Stack family or Brian Stack's wider circle of friends.
"It is plainly and utterly unacceptable that material that was potentially of evidential value to the investigation can no longer be located by An Garda Síochána," Martin said.
"It is admitted by An Garda Síochána that these are serious matters that had an impact on the investigation," he added. "As Taoiseach, and on behalf of the Government, I want to formally apologise to the Stack family for these failings."
Martin also stated that the Provisional IRA is "still in the possession of all the facts" on the case.
Brian Stack's son Austin Stack said the apology "means an awful lot to us."
"It's a great sense of comfort, to particularly my mother and to myself and my two brothers, because the state is officially owning up to the errors and the omissions that happened," he said.
Austin Stack said the serious crime review team found "194 errors and omissions" when it examined the first investigation. He added that the family had repeatedly requested access to the review report but had been refused.
"Every time we've requested it, we've been told that it's an internally valid document and that we cannot see it," he said.
He described Wednesday as "a very emotional day" for his family, and paid tribute to his father's service.
"My dad was doing a very difficult job at a very difficult time in our history," Austin Stack said. "He was awarded the Irish Prison Service's highest bravery award for that work that he was doing. And this is further vindication of him and his good name."
In the House of Commons on Wednesday, Secretary of State for Northern Ireland Sir Chris Bryant said he "warmly welcomed" the Taoiseach's apology. Asked about the matter by Democratic Unionist Party leader Gavin Robinson, Sir Chris said the apology was "entirely right and proper" and went to the heart of discussions MPs had been having as they debated the government's Troubles legacy bill.
He added that it was "incumbent on all of us to make fulsome and not mealy-mouthed apologies."
The IRA admitted killing Stack in 2013 after his family mounted a long campaign seeking answers.
