The teenager accused of murdering Alan Higgins allegedly admitted the morning after the fatal attack to stabbing the schoolboy, a witness told a jury at the Central Criminal Court.
Mr Daniel Whelan from Kilbarrack told the court that the accused allegedly said, "yeah, I stabbed him".
The accused, who cannot be named for legal reasons, denies murdering Alan Higgins (17), of Carraroe Avenue in The Donaghies, Donaghmede, on October 13th, 2002, outside the UCI cinema in Coolock, Dublin.
The accused also denies robbing the victim's mobile phone and a sum of cash on October 12th, 2002.
Mr Whelan told the jury that his brother is Anthony Whelan (18), who pleaded guilty, along with Michael Maher (18), to the manslaughter of Alan Higgins last Tuesday at the Central Criminal Court. Mr Whelan said the accused called into his house at around 10 a.m. on Sunday October 13th, 2002. "I looked at the teletext and it came up that some fella had been stabbed in the UCI the night before," Mr Whelan said.
The accused, he claims, asked him had he heard about the stabbing, to which the defendant allegedly replied, "well that was us".
"I asked him and he said 'yeah, I stabbed him'," Mr Whelan said.
Later that evening, Mr Whelan claims the accused, along with Maher and his brother Anthony, talked about the stabbing again.
"They said where they were that night and what happened, that's all I can remember," Mr Whelan said.
"They had what seemed to be Alan's phone, it was a Nokia red phone. They put it in a shore."
Mr Whelan said he "couldn't remember who put it in".
The State Pathologist told the jury that Alan Higgins died from "haemorrhaging and shock due to a stab wound to the chest".
Dr Marie Cassidy said the 17-year-old schoolboy "suffered considerable blood loss, so much had been lost that he developed a blood clot and blood was flowing from his wounds".
Dr Cassidy was shown a steak knife in court, saying "yes, that was the knife I was shown" in October 2002.
"Given the dimensions of the knife and the wounds to the body, a knife like this could have caused the stab wounds".
Dr Cassidy said Alan Higgins had a "severe form of leukaemia when he was four years of age". She said he had completely recovered from the illness and that "he was not suffering from leukaemia when he was fatally stabbed".
The schoolboy, Dr Cassidy said, also suffered "blunt force trauma to the head and arms" during the attack.
"The wounds to his face suggest Alan Higgins received a few punches to the face," the State Pathologist said.
The position of the fatal wound was in an "area normally protected" by the arm. "This suggests he had his arm raised in self-defence when he was attacked", Dr Cassidy said.
The 17-year-old victim had "received multiple blood transfusions", Dr Cassidy said.
The trial continues.