Two men were seen laughing after they took part in an attack which killed a homeless man, a court heard.
Matthew Heading, 41, died two days after he was brutally kicked and stamped on.
He died from a ruptured spleen in his room at Glenwood Lodge hostel in Grand Parade, Brighton.
One witness told police he was kicked "with the force of a David Beckham free kick" by one of his attackers.
Louise Golby-Burnett was on a bus on her way home from work when she saw part of the assault on June 21 last year.
She told a jury at Hove Crown Court that six men walked towards Mr Heading who tried to walk away.
Miss Golby-Burnett said four of the group stopped but the two men in front picked up their pace and caught up with him.
He was pushed to the ground by the alleged attackers who then turned round and started to walk back to the others.
She said Mr Heading said something to the two men who went back and started kicking him while he was on the ground.
Miss Golby-Burnett told the court: "They kicked him in the sides quite forcefully.
"The first man lifted his foot up and stamped on the head of the man on the ground.
"Then he jumped up in the air and landed with both feet on the guy's head.
"The man on the ground did not move at all. I don't know if he was in too much pain to move or was unconscious.
"The first man went back and kicked him a couple more times in the chest before leaving.
"Both men walked off and carried on chatting as if nothing had happened.
"They were even laughing but I don't know if it was about what they had done."
Adam Todd, 25, of Ropetackle Walk, Shoreham, Joe Budgen, 19, of Ann Street, Brighton, Martin Keating, 28, of Taunton Road, Brighton, Paul Hamlet, 32, of Falcon Court, Whitehawk, Brighton, and Oliver McNulty, 18, of New England Street, Brighton, all deny murder.
They also deny causing actual bodily harm to Joe Burton who was with Mr Heading when they were attacked.
Christine Laing, QC prosecuting, alleges that all the defendants either took part in the attack or encouraged the others to do so.
Philip Meredith, defending McNulty, asked Miss Golby-Burnett if any of the four others in the group had joined in the attack.
She said: "I don't recall any of the other four in the group.
"There was distance between them and the other two."
The trial continues.
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