A retired Garda superintendent said he had been concerned that a top RUC officer repeatedly used the same car to travel to the Republic in the months before he was killed in an IRA ambush.
Superintendent Bob Buchanan was murdered along with colleague Chief Superintendent Harry Breen near the border after a meeting at Dundalk Garda Station in March 1989.
Retired Garda Superintendent Pat Tierney, based in the town at the time, told the Smithwick Tribunal in Dublin that he met Mr Buchanan 12 times in both the North and the Republic between early February and the day he died.
“I certainly was a little apprehensive,” Mr Tierney said.
“I was conscious of the fact that he was coming quite often in the same car. It was a concern.”
The tribunal, established in 2005, is investigating allegations that Garda officers in the Republic or a civilian working in the force colluded with the IRA in the murders.
Mr Breen and Mr Buchanan were two of the highest-ranking RUC officers killed in the Troubles.
They had travelled to Dundalk garda station in Co Louth to discuss a possible joint RUC/Garda police operation against smuggling and were returning to the North when they were ambushed just north of the border on the Edenappa Road.
Mr Tierney, who was in charge of the Dundalk District office at the station, told the tribunal he had no evidence of any Garda or civilian collusion with the IRA.
Tribunal lawyer Dara Hayes said PSNI intelligence received more than 10 years after the killings claimed meetings between gardaí and the RUC were organised by a civilian administrator based at an unknown location in Ireland.
But Mr Tierney and another witness, former Garda George Flynn who also worked in the district office at the time, said they had no knowledge of this.
Mr Tierney said he spoke with Mr Buchanan on the morning of March 20, the day of the killings, during which the RUC officer said he wanted to arrange a meeting between Chief Superintendent Breen and then Dundalk Chief Superintendent John Nolan.
Mr Tierney told the tribunal the call was not “scrambled” and accepted it was possible the conversation could have been overheard.
He said he directed Mr Buchanan to Mr Nolan’s office.
The retired Garda superintendent said Mr Buchanan told him he was being transferred on April 17.
Mr Tierney met the RUC officer in Dundalk station that afternoon and said he was in a “joyous” mood at the prospect of moving.
“He (Mr Buchanan) was a very easy going man, easy to discuss with and talk to him, no formalities,” Mr Tierney said.
“A very nice man. A decent gentleman.”
Mr Tierney said he received a call from an RUC officer that afternoon expressing concern about Mr Buchanan and Mr Breen, after the officers had left the station.
Mr Tierney said: “(The RUC officer said) ’Pat, I wonder have our boys left.
“’There was an incident at Meigh. A red car was involved, we’re worried’ Words to that effect,” Mr Tierney said.
The retired top garda said he travelled to the border crossing and could see the RUC officers’ car on the road.
“We assumed the worst,” he told the tribunal.
Earlier, Mr Flynn told the tribunal he questioned the number of times Mr Buchanan travelled into the Irish Republic.
“They were strange times,” Mr Flynn said.
“I would be uncomfortable travelling north as often as he (Mr Buchanan) travelled south.”
The tribunal was adjourned until next week.