British security services tried to frame a Garda sergeant over the murder of two senior police officers from Northern Ireland to distract attention from their own collusion, an inquiry has heard.
Retired Sergeant Owen Corrigan said claims he passed on sensitive information to the IRA were a tactic by the British to switch the spotlight from their backing of loyalist paramilitaries.
Any other evidence against him in the long-running Smithwick Tribunal was down to gossip among police officers who had never met him, he said. "Policemen are gossips, by and large," he told the inquiry.
Mr Corrigan is the last witness to appear before the tribunal, which is investigating claims that some gardai colluded with the IRA gang that shot two Royal Ulster Constabulary officers in 1989. Chief Superintendent Harry Breen and Superintendent Bob Buchanan died in an ambush in south Armagh shortly after they left a meeting at Dundalk Garda station.
Mr Corrigan, based at Dundalk Garda station at the time, told the inquiry the only evidence against him was a statement by a British army agent Kevin Fulton, also known as Peter Keeley.
The claims were made to strengthen allegations of a link between Irish authorities and the IRA in the wake of substantiated allegations of British security service collusion with loyalist paramilitaries, the tribunal heard. "That is it in a nutshell," said Mr Corrigan.
The former detective said Mr Fulton continued to be paid by the British security services while in prison serving a two-and-a-half-year sentence for armed robbery.
The allegations that Mr Corrigan was involved in collusion were the most serious ever made during a tribunal in the history of the Irish state and the most serious ever levelled against any member of the Garda, he said.
Mr Corrigan said he was not in charge of border security at the time of the killings, but had always opposed RUC officers coming to Dundalk Garda station, for their own safety. The town was a hive of subversives, coming in and out of the station with documents to gather intelligence, he said.
The Tribunal heard Mr Fulton made a statement in September 2003 that he was in a house on the day of the murders and a man told him that Mr Corrigan was involved. His barrister Jim O'Callaghan said it "suited the intentions" of the British security services to link Mr Corrigan to the double killings.