Dozens of police officers have been involved in a brawl inside a Sydney court with a family on trial for brawling with police.

One officer was "smacked in the face" during the fight, witness and 2UE court reporter Leonie Ryan said.

A number of police cars circled the Downing Centre at lunchtime on Tuesday.

The fight broke out minutes after Adel, Hussain and Ali Mehanna were convicted of numerous offences, including affray, resisting arrest and assaulting police during a fight that broke out outside their Bankstown home on January 1, 2013.