The Special Criminal Court has accepted evidence identifying Patrick Hutch as one of the gunmen involved in the murder at the Regency Hotel in Dublin two years ago.
David Byrne was shot dead in the attack on 5 February 2016.
The prosecution claims Mr Hutch, of Champions Avenue in Dublin, was the man dressed as a woman carrying a gun on that day.
The 25-year-old denies charges of murder and related firearms offences.
The court also found that the gardaí involved in the identification and the process were truthful witnesses and there was no conspiracy or cover-up.
The issue that had to be ruled on at the Special Criminal Court today was over what happened when four gardaí went into a room at Ballymun Garda Station two days after the murder at the Regency Hotel.
Two detectives, Fergal O’Flaherty and Jonathan Brady, recognised Patrick Hutch in a photograph of a man dressed as a woman carrying a gun that day.
Both officers said they identified Mr Hutch separately and did not name him in each other's presence.
However, the defence claimed that because they were together in the room for a time, their evidence was tainted, the identification process was flawed and that they had tried to cover that up with false accounts.
Today, however, the three judges rejected this.
They found that while the two gardaí walked into the room together, and it would have been better if they had not, there was no reason to think that Det O'Flaherty had "blurted" out Patrick Hutch's name in front of Det Brady, whom they also found to be a credible witness.
The court found the garda who showed the detectives the images, Michael Ryan, to be a truthful witness.
It also accepted evidence by Detective Sergeant Pat O'Toole in relation to who viewed the image first, but could not accept beyond reasonable doubt all of his evidence.
The court also ruled today that there was no conspiracy to cover up a flawed or unfair process and no basis for excluding as tainted evidence the identification of Mr Hutch as a gunman.
The trial continues next week.