"Did she wonder where I was and why I wasn't there to help her?" said Tess Knight as she broke down in the NSW Supreme Court on Tuesday.

Ms Knight, her brother Michael Knight and Lisa Giles, who was one of Michael Guider's many child-abuse victims, read victim impact statements at the hearing of an application to keep him behind bars.

The now 68-year-old pleaded guilty in 2002 to the manslaughter of nine-year-old Samantha Knight, who went missing after leaving her Bondi home for school on August 19, 1886. Her body has never been found.

Guider's 17-year jail term has expired, but he is currently on an interim detention order.

NSW Attorney-General Mark Speakman is seeking a one-year detention order and a subsequent five-year extended supervision order.

When Guider was sentenced for Samantha's death, he was already serving time for numerous sex offences against more than a dozen other children between 1980 and 1996.

Ms Knight told Justice Richard Button that Guider showed no remorse for her daughter's death, continuing to drug and sexually assault a large number of children after he killed her.

She had "imagined thousands and thousands of scenarios, over and over and over again" about what happened to Samantha on the day she went missing.

"Was she so scared that she used the words of a younger child? Did she say 'I want my mummy'? Did she tell him 'I want to go home'?."

Ms Knight also wondered if Samantha was scared straight away, if she struggled, where she was taken, if she cried and whether she in pain as she was affected by the overdose of the drug Guider admitted giving her.

She had flashbacks about Guider's pornographic photos of children, which did not include their faces, which she had to scrutinise to see if she could identify her daughter.

Sometimes she wondered if images of Samantha had been shared and were still in circulation.

"Please don't release him into the community until the time comes when we have no choice," she asked the judge.

Ms Giles told the court Guilder would be a danger to the community if he's released.

"We are not physically safe if he is released - our children are not safe and our minds are not safe," she said.

"This is not a man who will fade into obscurity and potter humbly around his garden."

Guilder had infiltrated and manipulated her family and his long-term project "was me".

"His tentacles have such insidious reach," she said.

"He's not a one-trick pony and he's not finished yet."

Mr Knight said, if released, Guider should be banned from going to bushland, because that's where he may have buried his niece.

"My fear is that Samantha's remains could be a trophy for him or where she is would be a trophy for him," he said.

Forensic psychiatrist Jonathon Adams said he agreed Guider still posed a high risk of reoffending in a sexual way.

A relapse into sexual fantasies and urges if he saw children running around and had access to them was a matter of concern, he said.

However, psychologist Jenny Howell said she could not see any potential therapeutic benefit in keeping Guider in detention for another year.

Justice Button reserved his decision.

Australian Associated Press