The man who killed one of Australia's most prolific murderers has himself been found guilty of murder.
Matthew Charles Johnson, 38, had pleaded self-defence after killing underworld assassin Carl Williams in the high-security unit they shared at Barwon Prison in April last year.
But a jury rejected that plea and an alternative charge of defensive homicide, accepting the prosecution case that Johnson had murdered Williams by bashing him viciously with the seat post of an exercise bike as he sat reading a newspaper.
Johnson, who has spent most of the past 25 years in prison or juvenile custody, stood silently and calmly, seemingly resigned to his fate, as the verdict was announced and he was led away.
The verdict means a return to the scene of his crime - to a place he knows well.
It is the scene of a 1998 incident which can now be viewed as a rehearsal for his murder of Williams.
During the three-week trial, the jury heard, and saw, how Johnson walked up behind the unsuspecting Williams and bludgeoned him to death with an 80cm-long piece of pipe that resembled a small pickaxe.
The prosecution described it in its opening address as ''an ideal weapon''.
Johnson already knew that.
In 1998, he and other prisoners attacked and almost killed fellow Barwon inmate and triple murderer Gregory Brazel with a variety of weapons, including the seat post of an exercise bike.
The weapon clearly made an impression on Johnson, who told the court in his latest trial that he had deliberately ensured he had access to an exercise bike after sensing a problem may have developed between him and Williams.
Johnson also said he had strategically positioned a toasted sandwich maker in another part of their unit so he could defend himself against Williams if he needed to.
The same implement had also been used on Brazel 12 years earlier.
Johnson testified that he and Williams had known each other from earlier periods in prison and had been friends.
But when they moved in together after Williams was sentenced to multiple life sentences for murder, their friendship deteriorated.
Johnson, the head of a notorious group within Barwon Prison, known as the Prisoners of War, claimed the souring of the relationship was caused by Williams' bad attitude towards him.
''He forgot he was in jail ... he thought he was the boss of me,'' Johnson told the court.
The prosecution maintained the motive for Williams' murder stemmed from Johnson's hatred of ''dogs'', or police informers.
Justice Lex Lasry will sentence Johnson on a date to be fixed.
