Notorious Australian gangster Carl Williams was offering information to the police in the weeks before he was beaten to death in his jail cell, the trial of his alleged killer has heard. A lawyer who handled Williams' talks with the police said the gangster was preparing to provide the names of some of his underworld associates. The lawyer said Williams had become worried about his safety in prison. His former cellmate Matthew Charles Johnson, 38, denies murder. Johnson has admitted killing Williams, but said it was self-defence, adding that he was in a "kill or be killed situation". At the time, police feared the killing could spark another gangland war in Melbourne's criminal underworld. Williams was already serving a 35-year jail term for murdering three of his rivals when he was killed in April 2010. On the third day of Johnson's murder trial, Williams' former lawyer told the court that the gangster had been ready to tell police the names of other people involved in those murders. Shane Tyrrell said Williams had hoped to get his sentence reduced, as well as having his daughter's school fees paid, in return for the information. However, Mr Tyrrell said his client had become uneasy because prison staff had known about his talks with the police. On Wednesday, Williams' father George had told the jury that Johnson had killed his son because he wanted to benefit from the police deal. George Williams, himself a convicted drug trafficker, said Johnson had asked his son: "Can you get me on board?" Williams was one of Australia's most infamous gangland bosses before he was jailed. His life of crime and the gangland warfare it engendered in Melbourne was the inspiration for the TV series Underbelly.