One of seven Dubliners accused of beating a man to death said he hit him because he had pulled a knife on him and stolen his sister's phone.
The Central Criminal Court yesterday heard evidence of interviews with David Burke, who said he had tried to stop others assaulting the deceased.
Dale Creighton (20) was attacked on New Year's Day in 2014 on the footbridge over the Tallaght bypass near Saint Dominic's Road. He died in hospital the next day.
The accused, all of whom are in their 20s and from Tallaght, have denied murder.
They are Aisling Burke (23) and David Burke (28), of Beechpark, Collinstown, Co Westmeath; Graham Palmer (26), of Park Avenue, Portarlington, Co Laois; Ross Callery (23), of Gortlum Cottages, Brittas, Co Dublin; James Reid (26), of Glen Aoibhinn, Gorey, Co Wexford; Jason Beresford (23), of Coill Diarmuida, Ard a' Laoi, Castledermot, Co Kildare; and Gerard Stevens (27), of Grosvenor Square, Rathmines, Dublin.
Each also pleaded not guilty to violent disorder but Jason Beresford later changed his plea to guilty.
Garda Sinead McCormack said she arrested Mr Burke on January 2, 2014, and that he was interviewed at Rathfarnham Garda Station.
He said he was on his way home when he saw some men running around a corner. He said his sister also ran around the corner, screaming that they had her phone.
"I chased one of them," said Mr Burke. "He pulled a knife on me so I backed off."
He said other people joined the chase and that he saw a commotion on the bridge. "They had him held so he couldn't go anywhere."
He later discovered that the man he had chased didn't have the phone. "I legged it out of there. I didn't want anything to do with it," he said, denying in the early interviews that he had hit the deceased.
"They were all jumping in there to get at it," he said. "I was saying to stop."
He said only Mr Creighton had a weapon and that he "wasn't that bad" when he left.
He was then shown CCTV footage in which he was seen holding a steel rod or pole.
"The only reason I had it going on to the bridge was to protect myself."
Mr Burke was asked: "Did you assault him there?" "Yeah, I gave him a dig or two. I hit him for pulling a knife on me and robbing my sister's bag." He was asked if he had kicked Mr Creighton. "I kicked him in the leg as well."
He was later shown footage of Mr Creighton being lifted up and was asked if he looked OK.
"Not at all, but that's what I'm trying to say. I was trying to stop them. I picked him up about four times. You can see from the CCTV, I tried to keep everyone away from him."
He said he "lost it" when someone threw Mr Creighton down the steps of the bridge.
He said in his final interview that he was sorry he didn't stop the assault.
Garda McCormack agreed that Mr Burke had identified himself on screen trying to stop the assault, and agreed that notes of his interviews were handwritten and could not be a full version of what was said.
The trial continues.