The trial of 38 year-old Matthew Johnson, who has been accused of slaying convicted murderer and drug trafficker Carl Williams in HM Barwon prison in Geelong last year, enters its final stage as the jury begins to deliberate on its final verdict beginning on Tuesday.

ABC News mentioned that Bill Stuart, Johnson's lawyer appealed to jurors to take into account Williams' record as a notorious felon and the most dangerous person in the state of Victoria.

He said that Johnson must not be found guilty of murder charges on the grounds of self-defence.

Williams is the key figure in the Melbourne gangland killings and was sentenced to 35 years in prison with no parole for ordering the execution of 3 people and conspiracy to murder a fourth individual.

He allegedly sought the help of other people for contract killings in exchange for huge sums of money.

Williams was to be eligible for parole when he reaches 71 years.

In his testimony, Johnson said William was a "coldblooded and dangerous man who frightened him and bragged of having at least 15 people slaughtered."

Prosecutor Mark Rochford explained to the Supreme Court that Johnson should have sought a transfer if he was being threatened by Williams.

"It is not all about doing the world a favor by bashing the head of Williams," he added.

Williams was supposedly helping police authorities by furnishing police with information about former detective Paul Dale who was being probed for a double murder case, in exchange for a reduction in his sentence, according to the prosecution lawyer.

The prosecution also claimed that Johnson is the founder and so-called "general" of a group called Prisoners of War who despised inmates who cooperated with the police.

His motto was "death to the enemy" which was tattooed on his body.

Johnson's attorney countered by saying that Johnson had a lot of chances to kill Williams but never did anything until he found out that William was really planning to eliminate him.