Leslie Camilleri couldn't bring himself to reveal the most important secret about the disappearance of Melbourne teenager Prue Bird.

The notorious killer had already said everything he wanted to say.

When a Victorian Supreme Court judge invited Camilleri to reveal where 13-year-old Prue was buried, her mother Jenny, sitting just metres away, must have hoped he would finally solve the 21-year mystery.

But Camilleri, also known as one of the killers in the 1997 Bega schoolgirl murders, remained mute.

He has admitted killing Prue, who disappeared from her Melbourne home on February 2, 1992, but his version of what occurred is vastly different from that of prosecutors and witnesses.

Prosecutors say Camilleri, with the help of another man, Mark McConville, who is now dead, kidnapped Prue, held her hostage in a shed and killed her.

Camilleri, 43, says he strangled Prue in the street after she refused to tell him where her father was.

He pleaded guilty to murder last December, but after a four-day contested pre-sentence hearing this week the truth seems no closer to being revealed.

Inconsistencies were highlighted in the testimony of the key witness, who says she was held with Prue in an Ascot Vale shed.

And the court heard numerous versions of what happened to Prue.

On the first day of the hearing on Monday, Justice Elizabeth Curtain invited Camilleri to cleanse his conscience.

"He has come this far in the journey, he has pleaded guilty to murder, he has heard the prosecutor detail the various accounts that he has given to others as to where the body of Prue Bird was disposed of by him ... it might be time now for your client, this afternoon, to exercise his conscience such as it is and see if he can bring forth further information concerning the whereabouts of Prue Bird," she said.

Camilleri took the night to think about it. The next day Justice Curtain said she had received an email and Camilleri wished to speak to his lawyers.

But after he spoke with his solicitor the case continued.

Camilleri's hearing began 21 years almost to the day after Prue disappeared.

The front door of her Glenroy home was left open, the television was on, and her lunch, some corn, was uneaten.

It also appeared Prue had left the house without showering - something she would never do.

A witness saw a distressed Prue in a dark blue sedan banging with both hands on the window and yelling, "Help me," prosecutor Michele Williams SC said in her opening address.

The key prosecution witness is a woman known as Witness K, who claims she was held captive in a shed with Prue.

She told the court Prue had wanted to escape through a small window and was "quite distressed and upset" in the shed.

"(She) was just scared. She wanted to go home to her mum," she told the court.

"She wasn't understanding what was actually going on."

But there were apparent inconsistencies in the story she told about the shed.

Witness K told the court she woke up to find Prue gone.

But in a statement to police Witness K had said she was allowed to go free from the shed and Prue remained.

Evidence also showed that settlement on the property where the shed was located, owned by McConville's parents, did not occur until about two weeks after Prue disappeared.

Witness K also told how she had been in the car when Camilleri and McConville had discussed how they needed to kill a girl.

And how she had visited Prue's neighbourhood with the pair before her disappearance.

She was able to take police to the house in 2011.

During the hearing Camilleri, a large, tall man with a shaved head, often sat with his eyes closed and holding beads in his hand. The court heard he had converted to Islam while in prison.

He has told fellow prisoners he had personal reasons for not wanting Prue's body to be found.

Camilleri said when he was younger he was abused by two men and he killed one of them, burying the body near where Prue's lay.

He feared that if Prue's body was discovered, the body of the abuser would also be found.

He told a fellow prisoner he could not deal psychologically with the man's body being found.

In some of versions of his story, he said he believed Prue's father might have been one of his abusers.

Justice Curtain, who has the job of determining exactly how Prue disappeared, adjourned the matter to a date to be fixed, when further witnesses will likely be called.

AAP df/