A policeman ignored colleagues trying to control a mass brawl outside a mosque and instead joined in the fracas, a court heard yesterday.
Det Sgt Tariq Hussain was seen arguing with other Muslims while off duty and apparently hit a man repeatedly.
But when asked to help out by an officer he allegedly sneered at him and returned to the clash, which escalated into a 100-man punch-up.
Yesterday Hussain appeared in court with three other men charged with violent disorder and a fourth accused of affray.
Former officer Steven Mould told Birmingham crown court: "He was acting like an antagonist and yob."
Stephen Thomas, prosecuting, added: "Off duty he may have been, but he was asked to help restore calm and he just walked off."
The row was over a mosque leader in Burton-on-Trent, Staffs, last April. All five men deny the charges.
The trial continues.