AS the jury in the O. J. Simpson case started debating his guilt or innocence, Los Angeles was bracing itself for another onslaught of racial violence when the verdict comes in. The Police and Sheriff's Departments put officers on modified tactical alert as the jury convened, and an Emergency Operations Centre has been set up. With an eye to the riots that erupted after the acquittal of four white policemen in the Rodney King beating case, authorities are determined not to be caught unprepared again. Streets around the courthouse were being blocked off in the morning and evening, when the court convenes and adjourns. 'This is a precautionary step, so that when they come back with a verdict, we can very quickly gear up to a higher level of readiness,' said Bob Canfield, emergency preparedness co-ordinator for Los Angeles. 'We learned a tough lesson in the riots.' Los Angeles Police Department assistant chief Bavan Lewis added: 'There is no indication right now that anything is going to occur but we would be remiss if we were unprepared.' Until the verdict comes in, police officers will not be able to go home at the end of their shifts before they have checked if they are needed elsewhere. And half the sheriff's cars are ready to be reassigned at a moment's notice. When riots broke out in March 1992, the police department was harshly criticised for pulling out of the flashpoint South Central area during the first night of murder, arson and looting. Los Angeles Councillor Nate Holden, who is black and who represents South Central which was at the heart of the riots, has already appealed for calm, whatever the verdict. Schools are also taking precautions. Los Angeles education chief Sid Thompson has written to all heads of state schools warning that the verdicts 'have the potential of causing civil unrest'.