Detective Garda Adrian Donohoe was on an armed cash escort during a previous robbery at the same credit union where he was shot dead 17 months later, a trial has heard.
Evidence was given yesterday at the Central Criminal Court of an armed raid at Lordship Credit Union in August 2011 during which €22,500 was stolen in only 23 seconds.
The jury was told it is not the prosecution's case that Aaron Brady (29), on trial for the capital murder of Det Gda Donohoe, was involved in the earlier robbery.
Mr Brady (29) has pleaded not guilty to the murder of Det Gda Donohoe (41), who was then a member of An Garda Siochana acting in the course of his duty, at Lordship Credit Union in Bellurgan, Co Louth, on January 25, 2013.
The accused, of New Road Crossmaglen, Co Armagh, also denies the robbery of around €7,000 in cash and assorted cheques at the same location on the same date.
Credit union volunteer John Kenwright told the court he was working on the evening of August 5, 2011.
He exited the building with other staff at around 9.30pm and the front door was locked.
That evening, Mr Kenwright said, he was responsible for bringing the day's takings, totalling around €22,500 in cash and €35,000 in cheques, to Dundalk, where they were to be deposited.
The court heard Det Gda Donohoe was providing the armed cash escort for credit unions on the Carlingford Peninsula that night, but he was still at the Cooley branch when the robbery took place.
Mr Kenwright said that at the time it was normal practice for the staff member transporting the takings to sit in their car and wait for the armed escort to arrive from the other credit unions.
The witness said that two minutes after his colleagues had left the car park he heard a "high-powered" car drive up behind his own vehicle very fast, and it screeched as it came to a stop.
CCTV footage was played to the court which showed the black car entering the car park and exiting 23 seconds later.
Mr Kenwright said he looked at his side-view mirror and saw the driver get out and point a sawn-off shotgun at him.
The raider was shouting "give me the money" and a second armed man emerged at the passenger side door.
This man was also carrying a gun and smashed the passenger side window with the butt of the weapon, the court heard, before grabbing the money bag on the passenger seat.
Det Gda Stacey Linnane gave evidence of responding to a report of an armed robbery at Lordship Credit Union that night.
She said that during the course of the investigation she became aware that a black Audi A3 was stolen in a creeper burglary in Silverbridge, Co Down, earlier that day and used in the robbery.
This vehicle was later found burnt out in Co Down.
The 14-person jury was told the court would be dealing with legal issues in its absence and that it will be required again next week.