The son of a prison officer murdered 30 years ago has called on Sinn Fein president Gerry Adams to "take responsibility" for the actions of the IRA.
He believes senior members of Sinn Fein know who was responsible for the killing.
Brian Stack was chief prison officer at Portlaoise jail when he was shot in the back of the neck as he left a boxing match on the South Circular Road in Dublin on March 25, 1983.
Mr Stack was left paralysed and brain-damaged following the attack and died of his injuries 18 months later, aged 47.
Speaking to the Irish Independent before he attended a private meeting with Mr Adams at Leinster House, his son, Austin Stack, said the family "won't rest" until they find out who carried out the attack.
"We're looking for the movement, which he (Adams) has very strong contacts with, to take responsibility for their actions.
"We've all embraced the peace process, but for it to move on to the next level we would ask that they take account of the victims that never had answers," he said.
Asked if he believes Mr Adams was a senior IRA figure at the time of the murder, he said: "It's widely reported that he was and he's not in the position he's in by being a shrinking violet.
"I believe that he may know who is responsible for my father's death. I definitely believe people within his organisation know and people that are sitting around the parliamentary party with him know, both North and South."
The Louth TD has always denied being an IRA member and said it would be "remiss of me" to raise expectations that he or the Sinn Fein leadership could resolve matters for the family.
The initial garda investigation focused in particular on members of the Provisional IRA as the maximum-security prison at Portlaoise housed many Republican activists at the time.
He described the meeting as "productive" and said Mr Adams had agreed to "reflect on things", adding that both sides would meet again within the next month.
"Deputy Adams has agreed to help us in any way he can. We asked him to see what he could do within the confines of people he may know and contacts he may have to see if there was any way he could get us some answers.
"Nobody made any promises but Deputy Adams did agree to take on board what we had said. We felt he was genuine."
In a statement following the meeting, Mr Adams expressed his condolences for the family's loss and said he would "reflect" on what was said.
"Like many families, they are looking for closure and have borne their bereavement with great courage."