Senior gardaí in Donegal and Dublin doubted the reliability of an informer central to the investigation into the death of Raphoe cattle dealer Richie Barron, the tribunal heard yesterday.
Supt Joseph Shelly said he and Insp John McGinley met Chief Supt (now Assistant Commissioner) Dermot Jennings in 1997, and were told that Garda John O'Dowd had sent up several items of intelligence.
The superintendent said they were told the source wasn't reliable, and had given false information that led to a search of the farm of Mr Jim "Lofty" Gallagher.
Supt Shelly, Border superintendent in charge of intelligence gathering in the Donegal division, said he was surprised that so much information had been sent up that he didn't know about.
Intelligence was being "funnelled" through Supt Kevin Lennon.
He said he kept up to date by talking to sergeants in the division, and to Insp McGinley. This was described by tribunal barrister Mr Paul McDermott SC as "a back-door route".
Supt Shelly went on: "The type of intelligence we got with was very low grade. The C77 issue was dealt with through Supt Lennon. Very little of C77s came through my office." C77s are reports containing information on subversive activity.
Supt Shelly said he and Insp McGinley guessed the source was William Doherty, a petty thief. "It was much later in the year when Noel McBride told us what happened that the Barron connection became clear to us." Mr McBride made several allegations against members of the McBrearty family, which he withdrew in September 1997, blaming Doherty.
Doherty was sentenced in Letterkenny last week after pleading guilty to charges relating to the Barron investigation.
The tribunal also heard that a former Donegal garda could face two years' imprisonment for obstructing its inquiry. Philip Collins, who was stationed in Raphoe and involved in taking a key statement from Mr McBride, failed to obey a summons to give evidence at the tribunal.
The tribunal chairman said he would refer the relevant papers to the DPP.