Sex 'predator' not handling prison: court

A "predatory" child-sex offender who snatched young girls from Sydney streets is not handling prison well, a court has heard.

Richard John Crowe was jailed for a minimum of seven-and-a-half years, and a maximum of 12 years, last September for five brazen kidnappings and assaults on children between 1989 and 1991.

Labelled "predatory" by the sentencing judge, Crowe abused his victims, age nine to 17, in derelict buildings and storm drains, often wielding a knife and often telling the terrified children, "Scream and I will kill you."

The Crown has launched an appeal of Crowe's sentence, arguing it is manifestly inadequate.

At a hearing on Friday, Crowe's barrister asked the NSW Court of Criminal Appeal to take into account the prisoner's unique circumstances, including the fact that he had reacted badly to jail.

Barrister Belinda Rigg said Crowe, who has permanent frontal lobe damage and chronic, treatment-resistant schizophrenia, had been placed in protective custody.

He found prison "a terrifying place" and had extensively self-harmed, she said.

"It's clear for a number of reasons, his custody is more burdensome than (it would be) for someone not in his position," Ms Rigg told the court.

Ms Rigg also argued Crowe's sentence was not unjust.

She pointed to expert assessments, which found he posed a low risk of re-offending, partly because he had stayed out of trouble for more than two decades.

However, Crown barrister Nicole Noman argued Crowe's unusual case made it difficult to judge the risk he posed to the community.

"These are the type of kidnapping offences that... all parents fear happening to their children, and... that children have nightmares about," she said.

Crowe has pleaded guilty to a string of offences, including five counts of kidnapping, two counts of sexual intercourse without consent, and two counts of aggravated sexual assault.

He was arrested in August 2014, almost 25 years after his crimes.

He was not in court for the appeal hearing.

The three appeal judges reserved their decision.