Having served his time and with all legal avenues to keep him in prison exhausted, a convicted child sex offender and child killer will soon be released.

New South Wales Attorney General Mark Speakman has been in the midst of an extraordinary legal battle over recent months to keep 68-year old Michael Anthony Guider behind bars despite the fact the full term of his 23 year sentence expired in June.

AG seeking advice

Mr Speakman is now seeking urgent legal advice as to whether he can challenge a NSW Supreme Court decision to Mr Guider walk free later this week, but it seems unlikely that an appeal can be mounted in time.

Mr Guider was imprisoned on sixty child sexual offences in 1996, involving more than a dozen prepubescent boys and girls.

He had worked as a gardener and spent time "grooming" the parents of his victims, who let him babysit their children.

He took photos of the children and drugged some of them by lacing soft drink with sleeping tablets, before assaulting.

Mr Guider was already serving time when arrested and charged with the murder of 9 year-old Sydney girl Samantha Knight, who disappeared from Bondi in 1986.

He eventually pleaded guilty to manslaughter and received an additional sentence in 2002.

He has since denied killing Samantha and her body has never been found.

Supervision order granted

The NSW Government has been successful in having five years of supervision placed on Guider, despite the fact his parole period has expired.

However, it had hoped to have him held behind bars for at least another 12 months.

The extended supervision order is one of the toughest available in the law. Under section 6 of the Crimes (Serious Sex Offenders) Act 2006, an application can be made to the Supreme Court for an extended supervision order against a sex offender who, when the application is made, is in custody or under supervision, while serving a sentence of imprisonment.

The order against Mr Guider contains 56 conditions that are to be imposed upon his release — including a mandatory drug regime to reduce his sex drive.

He is also barred from changing his name or appearance, and his weekly schedule must also be provided to his parole officer three days in advance.

He will need to adhere to a curfew, will be banned from viewing pornographic material, and must participate in a drug and alcohol treatment program.

Opinion is divided

While a significant segment of the community is outraged that an offender like Mr Guider will soon be released into the community, others point out that he has served his full sentence and that to keep him in prison indefinitely would undermine the rule of law as well as certainty in sentencing.

Those supporting his release further point out that his supervision conditions are the most onerous ever imposed, and that he will therefore have little opportunity to reoffend, even if he is so inclined.

Further supporting his release are observations by NSW Supreme Court Justice Button, who was presented with evidence from three experts in psychology and psychiatry that unanimously concluded the risks of Guider re-offending could be "reasonably managed under a stringent and lengthy system of supervision in the community".

Guider has been "model" prisoner" who received just one warning in more than two decades behind bars, for feeding birds. He has taken part in day release without any issues, participated in three sex offender treatment programs, completed a university degree, and undertaken drug and alcohol interventions as well as an anger management course.

But victims groups are not convinced Guider is reformed, and believe that despite the extensive conditions on his release, he is likely to reoffend.

They say keeping him behind bars is not about punishment, it's about prevention.

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