A lack of access to crucial MI5 intelligence is hampering Garda attempts to find the mole in its ranks who the Smithwick Tribunal says colluded with the IRA in the murder of two RUC officers.
That intelligence, presented to the tribunal at a late stage, was a key factor in determining the outcome of the eight-year inquiry.
It was outlined in private session to Judge Peter Smithwick by a PSNI assistant chief constable. But it is understood it was collected by agents from MI5 during an operation along the border.
The intelligence was described as "live and of the moment" but was dismissed by a senior counsel for Garda Commissioner Martin Callinan as "nonsense on stilts".
The Smithwick findings, which rocked the gardai, have cast a cloud over Dundalk station where RUC Chief Supt Harry Breen and Supt Bob Buchanan had been visiting for cross-border security talks before they were ambushed and murdered by IRA units.
Gardai are now anxious to uncover the identity of the person or persons blamed by the tribunal for a leak of information leading to the deaths of the two officers.
But their lawyers were given no opportunity to either examine or challenge the evidence because they were excluded when the information was given.
Gardai are examining their position on whether they can seek access to that intelligence to allow their 'mole hunt' to make progress.
The Garda position was spelled out on the last day of the hearing by counsel Diarmaid McGuinness.
He pointed out that PSNI Assistant Chief Constable Drew Harris had told the tribunal there was no RUC intelligence at the time of the murders that suggested collusion by any member of the gardai in the ambush.
But now, 24 years later, the tribunal was faced with a wealth of intelligence, which was said to exist and to be all accurate.
The Smithwick Inquiry found that gardai colluded with the IRA in the murders of two senior RUC officers, Chief Supt Harry Breen and Supt Bob Buchanan. The officers were ambushed and shot in south Armagh in 1989 after a meeting with gardai in Dundalk. However, Judge Smithwick did not point the finger of blame at any individual Garda officers in relation to the murders.