Michael Anthony Guider, 68, initially suggested aliens or white slave traders were behind the 1986 disappearance of the Bondi girl before eventually pleading guilty to her manslaughter in 2002.

Guider's 17-year maximum term expires on June 6.

Hearing a last-ditch bid on Monday to keep him behind bars, the NSW Supreme Court was told his story about Samantha had changed again.

"He will deny it to his dying day," Justice Richard Button said, quoting a recent medical report.

Samantha, whose body has never been found, was one of more than a dozen children Guider abused between 1980 and 1996 and one of those drugged with sleeping medication to facilitate his abuse.

The sentencing judge for Samantha's unlawful killing labelled the former gardener and part-time babysitter "a compulsive and committed paedophile who has little, if any, insight into the consequences of his behaviour".

The court on Monday was told Guider now claims his confession was made under pressure from police and others.

David Kell, representing the State of NSW, said Guider had a chronic history of abusing young girls and boys, often after endearing himself to their parents.

"(Even after Samantha's death) it did not cause the defendant to cease using the drug on other children," he said.

He argued Guider should not be released until at least August, when a decision is expected on whether he should be subject to a one-year detention order and subsequent five-year supervision order.

Guider's barrister Matthew Johnston said the pedophile had been a model prisoner and should be released on an extremely strict supervision order, which would have dozens of conditions and force him to live at a halfway house next to Long Bay jail.

The prison, where Guider is held, is eight kilometres from where Samantha Knight was last seen 33 years ago.

Mr Johnston added the determining factor before Justice Button wasn't Guider's guilt but whether the supervision order was sufficient to protect the community.

"He is a prisoner worthy of the next step of being tested under strict supervision," Mr Johnston said.

The court was also told Guider has been granted 20 day-leaves under the supervision of a chaplain, prompting a reaction from some in the public gallery.

Samantha's mother Tess Knight said she had only learned of the day releases a few days ago.

"I have been told it's part of a normal process and yes, I would have liked to have been told that," she told reporters outside court.

Justice Button will deliver his decision before June 6.

Australian Associated Press