SLAIN underworld figure Carl Williams told his lawyer he didn't trust prison staff in the lead-up to his death in custody.
Fellow Barwon Prison inmate Matthew Charles Johnson, 38, has pleaded not guilty to murdering Williams last April, claiming he acted in self defence when he bashed his cellmate with an exercise bike stem.
The killing was caught on CCTV but prison staff did not discover Williams had been attacked until alerted by Johnson some time later that Williams had 'hit his head'.
The Supreme Court heard Williams had been cooperating with police and feared it made him a potential target in jail.
His barrister Shane Tyrell told the jury Williams was worried about publicity of his involvement with police.
"He was not ... trustful of the prison guards," Mr Tyrell said.
But Williams had no such concerns about his two cellmates, Johnson and old friend Tommy Ivanovic, who was a godfather to Williams's daughter Dhakota.
