Quaddus Ali, then 17, suffered a brain haemorrhage and was admitted to a hospital's intensive care unit.
John Rutter, 22, a council caretaker, of Stepney, east London, who denies affray, allegedly later confessed to one of his superiors at work that he had taken part in the general violence that night.
John Williams, for the prosecution, said it was the Crown's case that Rutter had admitted to his superior that the attack in Stepney, east London, in September 1993 was on a group of Bangladeshi youths who had caused problems for his younger sister.
The jury was told that as police closed in on Rutter he left his job with Tower Hamlets council and went to Norfolk. He was arrested just before Christmas that year.
Mr Williams said the attack took place just outside the Dean Swift pub in Commercial Road. Four Asian youths, including Mr Ali, now 18, were waiting for a friend near by when trouble started.
Two managed to escape. One of the others who ran off was caught and kicked to the ground, but he suffered only bumps and bruises.
Mr Ali was "subject to what was no doubt, on any view, an extensive and exceedingly nasty and vicious attack", said Mr Williams. He was rendered unconscious. He suffered a haemorrhage to his brain and had to be treated in an intensive care unit."
He said evidence from onlookers and people driving past suggested the Asian youth was "repeatedly stamped upon".
Mr Williams told the jury that afterwards Rutter went with his younger sister Laura to the home of a friend and his superior at work, Carl Lynch.He said Mr Lynch had been told of a previous incident involving Laura and some young men.
"The Crown's case is that John Rutter told Mr Lynch that he had been involved in a fight outside the Dean Swift public house ... and that it involved those whom he said had been responsible for the incident with his sister. The Crown's case is that the attack he had been involved in ... was not necessarily the precise attack on Mr Ali but the general series of events," said Mr Williams.
Rehan Uddin, who lives near by, told the court how he saw his friend being attacked as he lay on the ground. "Two guys were kicking him on the floor. I think he was lying face down. The kicks ... were hitting him about the upper body and head."
He ran out of his house to help and the two men fled.
"I was checking his body for any stab wounds, but he was clear. I was talking to him but he was not responding and I realised he was unconscious. There was no sign of any injuries," Mr Uddin said.
The trial continues today.Reuse content