Irish prison officer Brian Stack was “badly failed” by the investigation into his murder in the 1980s, the Taoiseach has said as he delivered a State apology to his family.

Mr Stack, the chief prison officer in Portlaoise, was shot in the neck by the IRA in March 1983 and died 18 months later.

On Wednesday, Micheal Martin delivered a State apology to the Stack family and said: “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 Siochana.

“It is admitted by An Garda Siochana that these are serious matters that had an impact on the investigation.

“As Taoiseach, and on behalf of the Government I want to formally apologise to the Stack family for these failings.”

Failings included not keeping a map made of the crime scene or a motorbike helmet linked to the crime, as well as a lack of custody of exhibits including samples, debris and fingerprints.

Mr Martin also outlined other shortcomings in documenting aspects of the original investigation including whether prisoners and prison officers were interviewed, adding that Mr Stack’s family and wider group of friends were also not interviewed.

No-one has been brought to the justice for the murder of Mr Stack.

It was not until 2013 that the IRA admitted responsibility for Mr Stack’s death, the only prison officer murdered in the Republic during the Troubles.

He was left paralysed and brain-damaged by the shooting as he crossed a road outside a boxing event at the National Stadium in Dublin in late March 1983.

He suffered for 18 months before dying from his injuries at the age of 49.

Mr Martin said: “We know now, because of the work of his family, that Brian was targeted and shot by members of the Provisional IRA, an organisation still in possession of all the facts of what happened.”

He added: “Brian and his family – a man who was providing a hugely important service as chief officer at Portlaoise Prison at a time of great peril for the State – was badly failed by the investigation into his killing.”

During statements in the Dail around the apology, criticism was also levelled at Sinn Fein by Labour leader Ivana Bacik.

Ms Bacik said: “As we all know, there are people – there must be people – who know who Brian Stack’s killer or killers were or are.

“Indeed, it’s been alleged that former members of this House either knew who the killer was, or indeed possessed information that would have been material to an investigation into the killing.

“In this context, as we know, on 7 December 2016, former TD and leader of Sinn Fein Gerry Adams made a Dail statement – a personal explanation by a member – on the murder of Brian Stack.

“It’s very rare for the Dail to give a member time for a personal statement, and it’s the Labour Party’s view that Gerry Adams wasted that opportunity in failing to provide the Stack family with substantive answers in that statement.”

Sinn Fein TD Pearse Doherty said the “hurt caused by republican actions must be acknowledged and that suffering cannot be disowned”.

He made the remark as he welcomed the apology on behalf of Sinn Fein and offered “sincere sympathies” to Mr Stack’s family.

He said: “The shooting of Brian Stack was wrong; it should never have happened. His family suffered a terrible loss. The failures in the investigations compounded that suffering and left them seeking answers over many decades.”

He added: “In 2013, a former IRA leader acknowledged that IRA volunteers were responsible for the shooting of Brian Stack and said it should not have happened, and expressed sorrow to the family.”

Mr Doherty told the Dail that other families are also seeking answers over Troubles-era killings and said: “As an Irish Republican, I believe that building a better future requires us to face the past with honesty.

“People from all walks of life and every background suffered through the actions of British state forces, republicans – including the IRA – and unionist paramilitaries. The hurt caused by republican actions must be acknowledged, and that suffering cannot be disowned. I am sorry for all the lives lost during the period of conflict on this island, without exception.”

Earlier, Mr Martin said the garda investigation established in 1983 failed to identify those responsible and a review by the Garda murder squad found nothing of evidential value.

After this point, the investigation into the killing remained open but dormant.

Mr Martin said that following a request of the Stack family, the Garda Commissioner directed a review of the case in 2007 by the Garda Serious Crime Review Team.

He added: “This review made 202 recommendations relating to the case, leading to the Garda Commissioner directing that an independent re-investigation team be appointed in the National Bureau of Criminal Investigation in 2008.

“Although this brought a fresh impetus to the investigation and led to the identification of new lines of inquiry and suspects, it also led to the identification of a number of serious failings and shortcomings in the management of the earlier Garda investigation.”

Mr Martin said these failings were admitted by An Garda Siochana in 2019.

He added: “Although it is clear that there was a strong suspicion of Provisional IRA involvement on the part of investigators both in the original investigation in the 1980s and the re-investigation since 2008, there was a failure by gardai to identify a definitive link to the Provisional IRA in the shooting until this was admitted to Austin and Oliver Stack by a former IRA commander in 2013 through their own family efforts to uncover the truth.”

Mr Martin said relevant intelligence received by gardai in 1990 was also not recorded on the original investigation file and later brought to the attention of investigators by the Stack family in 2016.

He said Mr Stack served the State with distinction and told the Dail the failings raise “legitimate concerns about how the investigation was conducted and whether it was done competently and properly”.

He added: “This is an inherently unfair position to place the Stack family in, and today I also apologise for this.”

Mr Stack’s wife Shiela and sons Austin, Kieran and Oliver were in the distinguished visitors’ gallery for the debate, having earlier met Mr Martin at Government Buildings.

The Taoiseach said: “They have campaigned tirelessly to uncover the truth of what happened to Brian in March 1983, to keep his memory and legacy alive following his death in September 1984.

“Unforgivably, we still don’t have the full truth of or any justice for what happened that day.”

In 2019, Austin Stack said the family found “some closure” when then-Garda commissioner Drew Harris offered an apology for failings and shortcomings in the investigation into the killing.

Mr Martin said gardai continue to pursue live lines of inquiry in the case.