Detectives are conducting a fresh round of interviews with the family of murdered prison officer Brian Stack as they attempt to identify the senior IRA figure who admitted the terror group was behind the 1983 killing.
Officers from the National Bureau of Criminal Investigation (NBCI) are attempting to build a profile of the man, who met the victim's sons Austin and Oliver Stack at an undisclosed location along the Border in August 2013.
The meeting was organised by Sinn Féin president Gerry Adams, who brought the Stack brothers to meet the IRA leader in a blacked-out van.
It's understood gardaí met with Austin Stack for six hours in recent days as they stepped up their inquiries.
It's now expected that gardaí will also interview Mr Adams, who has to date refused to tell the name of the individual who confirmed the IRA's responsibility.
Opposition TDs have said that any refusal to pass over the man's name to the gardaí would represent an obstruction of a live murder investigation.
However, Mr Adams has said that the meeting was predicated on the principle of confidentiality and that he does not intend to breach that agreement.
Gardaí are understood to have the names of a number of senior republican figures who they believe may be able to help the investigation.
Further interviews are expected to take place in the coming weeks in a bid to identify the IRA figure.
The man was not disguised when he handed the Stack brothers a statement, in which the IRA expressed regret for the killing of their father.
The IRA leader also revealed that a man had been disciplined following an internal IRA investigation.
The meeting took place in a house which gardaí believe may be located just across the Border from Co Louth.
Last night, Austin said he will not give up his fight for justice for his family.
"It is incredible that as we enter 2017, the leader of a political party can put on record in the Dáil that he will not co-operate with a murder inquiry," Mr Stack told the Irish Independent.
"The most basic principle of republicanism is that all citizens are treated as equals.
"In this instance, Gerry Adams wants to be treated differently to other citizens. He wants different standards to be applied to him than any other citizen."
The issue of the Stack case has been discussed among senior ranking gardaí after Mr Adams sent an email to the Garda Commissioner on February 23.
In the email, Mr Adams named four individuals who he said may have information in relation to the murder, which took place outside a boxing stadium in Dublin.
Two of the individuals - deputies Martin Ferris and Dessie Ellis - were named in the Dáil by Fine Gael TD Alan Farrell. Both say they have no information about the murder.
The third individual named is a very senior Sinn Féin politician who plays a direct role in devising party strategy.
The fourth man served as a senior IRA commander in Dublin. He recently returned to the capital where he is facing charges for other alleged offences.
In a post on his blog, Mr Adams suggested he may not be able to assist other families seeking closure as a result of the Stack family.
"In the absence of a formal truth recovery process I agreed in 2013 a confidential process with the Stack brothers to secure for them acknowledgement and information about who killed their father," he wrote.
"Could someone please tell me how they expect a truth recovery process to be implemented if I break my word? Why would anyone, IRA volunteer or British soldier, RUC officer, or Unionist paramilitary, or British or unionist politician ever contemplate speaking about their role in the conflict?"