Stephen Agbedi (19) gave evidence yesterday that while he was on a green area with others they heard raised voices and his friend Bobby Kuti shouting "Why are you calling us n******?".
He said punches were thrown and he went to help get Bobby away from Michael Barry and his brother Paul (39)
He said they all ran away when a baseball bat was produced by Michael and later saw a black Nissan jeep approach them with the two men in it.
He said Paul Barry got out of the jeep and pointed a knife at Gracia Lulendo, when Toyosi ran over to him and Paul turned to him and stabbed him in the chest.
"Toyosi was running and holding his chest saying "Boys, he stabbed me. Boys, he stabbed me," said Stephen.
He said dialled the emergency services when Toyosi fell to the ground.
Addressing the jury on the opening day of the trial, counsel for the prosecution, Brendan Grehan, said it was the prosecution's case that Michael Barry's now deceased brother Paul (39) murdered Toyosi and that Barry was an accessory to the murder.
"Michael Barry's actions are that he was clearly supportive and facilitated the killing and in those circumstances it is the prosecution's case that he is guilty of the offence of murder even though he did not carry out the act of murder itself," said Mr Grehan.
The jury heard that the victim was with four black males and five white females when they passed a green area outside Paul Barry's brother house at Mount Garrett in Tyrrelstown.
Counsel said one of the girls asked Michael and Paul for a light for a cigarette which resulted in a row, with racist undertones including the words 'n******' being used.
Bobby Kuti took offence and threw a punch at the Barry brothers. The prosecution said Michael and Paul Barry called for weapons to be brought out from the house by Paul's partner Colette Murphy and a baseball bat was given to the accused.
"There is no suggestion that the accused struck anyone with the baseball bat but appeared to have been pivotal in ending the initial incident as the young group then ran away," Mr Grehan told the jury.
In the aftermath, Michael Barry discovered his mobile phone had gone missing and drew the conclusion that one of the youths had taken the phone.
He decided to try to retrieve it and got into a Nissan Quas Qai jeep with Paul, who had been drinking. They came across the group at the Boulevard roundabout.
Prosecution counsel said Paul Barry got out of the jeep and chased one of the black youths with a knife.
Toyosi came to help his friend and, in an attempt to intervene, Paul Barry swung around and the knife ended up in Toyosi's chest. It is the prosecution's case that Barry withdrew the knife and went back to the jeep and Michael Barry drove away from the scene.
Mr Grehan said neither the mobile phone nor the knife had ever been recovered or identified. The trial continues.