A suspect in a boxing weigh-in murder stayed at the Dublin hotel where the shooting happened the night before, court documents have alleged.
Kevin Murray (aged 46) was preparing for his role in the killing the following day, a warrant for his arrest submitted by the Irish authorities claimed.
Murray was refused bail by a judge in Northern Ireland. He is sought by Irish prosecutors on suspicion of murder and fire arms offences and is fighting extradition after he was arrested in Strabane in Co Tyrone this month.
David Byrne (aged 33) was gunned down and two others were injured during last winter's attack and details of the warrant for Murray's arrest were disclosed by Patricia Smyth, the Recorder at Belfast court.
She said: "The requested person stayed overnight at the Regency Hotel on 4 February 2016.
"The warrant alleges that this was in preparation for his role in the murder the following day."
The warrant also claimed Murray had been identified in security camera footage of the scene by several police officers on both sides of the Irish border.
The senior judge said the severity of the offences alleged against the accused, of Townsend Street, Strabane, was relevant to the decision not to grant bail.
She also based her ruling on the ability of the Prison Service to care for his health needs.
He walks using a mobility aid and has undergone brain scans after his health degenerated in recent months, lawyers told the court. The accused is unemployed and separated from his wife.
The judge said detailed evidence was contained in the European Arrest Warrant issued by Irish authorities.
It said a second alleged member of the gang, Patrick Hutch, had been identified and had separately been charged with murder.
Ms Smyth said the director of public prosecutions in the Republic had directed that Murray be prosecuted.
The judge said the accused had made clear that he would not cooperate.
The accused was not in court due to an administrative mix-up but some of his family attended and were willing to provide a surety to the court had he been released.
The judge said the issue of bail may be revisited once more medical evidence was available.
She said: "I am satisfied that there are substantial grounds for believing that the requested person, if released on bail... would abscond."
She remanded him in custody, with the case to be reviewed later this month.