Aaron Brady has been found guilty of involvement in the robbery that led to Det Garda Adrian Donohoe being shot dead in Co Louth more than seven years ago.
The jury of five men and seven women will continue their deliberations on Tuesday on the charge of capital murder which Brady has denied.
At 1.33pm, after 12 hours and 35 minutes considering their verdict since last Wednesday, the foreman of the jury announced that it had reached a unanimous verdict that Brady is guilty of robbery.
Mr Justice Michael White asked the jury to return to the Central Criminal Court on Tuesday, and said he will accept a majority verdict in relation to the capital murder charge if at least 10 of the 12 jurors agree.
Brady (29), from New Road, Crossmaglen, Co Armagh, had denied involvement in the robbery of €7,000 at Lordship Credit Union in Bellurgan, Co Louth, on January 25th, 2013.
He has also pleaded not guilty to the capital murder of Det Garda Donohoe at the same location during the robbery.
During the trial the jury heard that four men jumped over a wall surrounding the credit union car park as employees prepared to leave with the day’s takings from several rural credit unions.
The prosecution has alleged that Brady was the gunman who fired a single shot that fatally wounded the detective.
Brady told the trial that he was at a diesel laundering yard on Concession Road in south Armagh when the robbery took place.
Verdicts
Mr Justice White has previously told the trial that there are several possible verdicts in relation to the capital murder charge.
If they are satisfied that the prosecution has proven beyond reasonable doubt that Brady was the gunman, for capital murder it must also be proven that he knew he was shooting a member of An Garda Síochána acting in accordance with his duty or was reckless as to whether it was a garda.
If they accept that he was the gunman but are not satisfied that capital murder is proven they can find him guilty of murder or guilty of manslaughter.
Manslaughter, the judge said, is an unlawful killing where the accused person did not intend to kill or cause serious injury.
The defence raised the possibility of manslaughter on the grounds that the shooter may have been attempting to fire a warning shot.