Detective Garda Adrian Donohoe was murdered as part of a nifty, well-planned robbery that was carried out for "criminal reasons" to raise money.
Donohoe, along with his colleague Detective Garda Joe Ryan, was on a routine cash escort on the night of his murder.
Senior Counsel Brendan Grehan described said the robbery was "a very slick operation, highly organised, with a lot of people working together as a team".
Prosecutors opened the trial of Aaron Brady in front of the Central Criminal Court on Tuesday, saying the seasoned detective was blown up close by a shotgun and died immediately. "There is no suggestion of a connection with any cause".
He said by his own account Aaron Brady spent the day entirely with two other men in their 20s, one of whom's auto was noted driving past the Credit Union on the day. The lawyer said there would be evidence that Mr. Brady had financial concerns ahead of the robbery and indicated to others that these concerns would soon go away.
Justice White also said that the alleged offences occurred on the Carlingford peninsula, and involved events in Dundalk and "quite near" south Armagh.
All of the evidence is circumstantial, but Mr Grehan finished by telling the jurors he was confident they would be satisfied that Aaron Brady was guilty of capital murder and robbery. The prosecution says this is also a lie. Armagh has gone on trial accused of his murder in 2013, and he is also charged with robbery.
He settled in NY "believing he was beyond the reach of the law" and had "various conversations with people" there.
The judge in the trial of a man who denies the capital murder of a garda has told the jury to put emotion and sympathy aside when considering the facts of the case.