Those who sign up for CUBIT are more likely to be released on parole, Corrective Services Commissioner Peter Severin told a court this year. Corrective Services says the $1.4 million a year program is world-best practice, based on good evidence from large international meta-studies. But there are doubts as to whether psychological treatment of its kind can reform a sex offender. "If only it were true, but it's fanciful," says forensic psychiatrist Jeremy O'Dea. The NSW Auditor-General in May found a lack of evaluations to support Corrective Services' therapy programs.

A crime statistics study last year found "no evidence" that CUBIT reduced sexual reoffending, criticising the methods of a previous study that found a steep drop. Britain this year scrapped its current group therapies after finding they slightly increased some sexual reoffending, possibly through the normalisation of deviant fantasies. And the independent medical review Cochrane found no robust evidence that psychological interventions kept more sex offenders out of jail. Without urgent new trials to test effectiveness, "society is lured into a false sense of security in the belief that once the individual has been treated, their risk of reoffending is reduced", the authors wrote. At the same time, prisoners are being released into community supervision on the condition they undergo "chemical castration", a catchy title for testosterone suppressants. But these, too, have been attacked for a lack of evidence and one opponent argues judges have been misled to believe they work. The large gaps in research raise a troubling question about government policy: are sex offenders being released treated but unchanged?

Two studies, two very different stories Sydney's Long Bay Jail has been home to CUBIT since 1999, managing dozens of inmates at a time in special units. Over four sessions a week, for nine to 12 months, they talk with psychologists and among themselves about what drove them to offend, their alcohol and other drug problems, and their antisocial attitudes. They learn about coping mechanisms and plan for the healthy, responsible lives they might lead on the outside. The model is cognitive behavioural therapy – the same kind used to treat depression and anxiety – and emphasises relapse prevention. Two studies have examined CUBIT, and tell very different stories. A 2010 peer-reviewed study by Corrective Services found sex offenders who completed the program reoffended at a rate of 8 per cent. That was compared to a projected 26 per cent of untreated offenders with the same risk profile, according to a statistical tool used by the authors.

The results suggest an outstandingly successful program, one that would save many children, women and men from horrendous crimes. "It certainly is promising early research," says co-author David Bright, now an associate professor of criminology at Flinders University. Bright acknowledges the limitations of his study (including its small sample size and limited follow-up time) while saying it supports the same conclusion as international meta-studies. For instance, a 2002 review by North American researchers found a 28 per cent decrease in reoffending among sex offenders who received psychological treatment. The second study into CUBIT, released by the NSW Bureau of Crime Statistics and Research last year, found nothing like the 70 per cent drop recorded by the first. It found no drop at all.

The second study criticised the risk profiling of the Corrective Services research, which is based on Canadian and UK samples. But it warned against drawing a firm conclusion that CUBIT was ineffective, given its own small sample size. "BOCSAR did the best they could under the circumstances," says Danielle Matsuo, Corrective Services' director of statewide programs. Asked whether the department's own study was superior, Matsuo declines to say, citing the difficulties of comparing "apples and oranges" methodologies. She says CUBIT is based on "the best evidence we have" from large-scale meta-studies, allowing many offenders to change their attitudes, and parole decisions justifiably take participation into account. "Simply incarcerating somebody and not providing programs and services can actually have a more detrimental effect i.e. make them higher risk."

It is notoriously difficult to investigate sex offenders' recidivism. Few "gold standard" studies – randomised controlled trials – have been conducted anywhere in the world. There are ethical concerns about depriving prisoners of treatment to create an experimental comparison group. And, contrary to the tabloid image of the sex offender who commits new crimes at every opportunity, the rate of reoffending is low compared to other offences. That makes it harder to spot statistically significant effects. But the NSW Auditor-General, while finding Corrective Services relies on "robust" international research, has called for independent re-evaluations of all programs. "Corrective Services NSW does not have enough evidence to show that program participation reduces reoffending," the report said. 'Smooth psychopaths who turn on the tears' Maurice van Ryn, who was jailed for paedophilia offences, said anti-libido drugs freed him of his deviant sexual urges.

Several leading forensic psychiatrists in NSW are particularly scathing of purely psychological interventions. "The sexual offender treatment industry, and I call it an industry, is like the military industrial complex, it's just got a life of its own," says Olav Nielssen, a senior research fellow at Sydney University. "I tell you who does well in CUBIT: smooth psychopaths who turn on the tears, can act all contrite and do all the homework, say they're sorry." Nielssen has much more confidence in "devastatingly effective" anti-libido drugs, which he has prescribed to 20 to 30 patients alongside traditional psychotherapy. Corrective Services supports the use of anti-libido drugs, which are meant to lower a patient's sex drive, for a select group of high-risk offenders. In the past year, 15 prisoners have received the drug Androcur, the only one available on the Pharmaceutical Benefits Scheme. Maurice van Ryn, the former Bega cheese boss jailed for paedophilia offences, told a doctor the drugs had freed him of his deviant sexual urges. "The tragedy of all of this is, you don't see ads on television [that say], if you are this way [sexually attracted to children], you can do something about it," he said.

Jeffrey Wayne Davie, a serial paedophile who used his position in the Boy Scouts to target his victims, has agreed to begin a course. In May, Supreme Court Justice Stephen Rothman allowed Davie, who posed a "very high risk (unmedicated) of reoffending", to be released into the community on an extended supervision order (ESO) so long as he started taking the drugs a month before. "In the absence of anti-libidinal treatment that is effective, supervision that could be undertaken in the course of an ESO, would be insufficient to sufficiently ameliorate the risk associated with his release," Justice Rothman found. But anti-libido drugs have their sceptics, too. A meta-analysis of child sex offender studies published in The British Medical Journal found "major weaknesses in the scientific evidence" for both psychological and medical interventions.

The Cochrane review of anti-libido drugs found the evidence to support a reduction in sexual reoffending was "sparse" and "poor". A forensic psychiatrist with 25 years' experience, O'Dea says he has treated many hundreds of sex offenders in Australia and overseas with anti-libido drugs. "I use the example of eunuchs, of the old harems," he says. "The sheiks didn't set the eunuchs aside and give them a stern talk and say 'Now I don't want you to interfere with any of my ladies'. They castrated them." O'Dea says the Cochrane review is well known for its conservative approach, excluding almost all research except randomised controlled trials. He points to surgical castration studies from continental Europe from the first half of the 20th century and a number of recent clinical studies to suggest anti-libidos work. Then there is his own clinical experience.

"I've had many patients, particularly when you take the anti-libidinal medication, say 'For the first time in my life, I'm free of these intrusive, distressing sexual urges and I feel so much better for it'." However Chris Ryan, a Sydney University psychiatrist, says physicians are notably poor at gauging the efficacy of their own prescriptions, while the studies into anti-libido medications are "almost universally bad". "Various judges have been persuaded that this will keep the public safe and there's just no evidence for that," he says. "I regard those practitioners as misleading the court." Maggie Hall, a criminal lawyer and criminologist at Western Sydney University, says doctors are prescribing a drug with sometimes severe side effects, including liver problems, without the evidence to justify it. "I don't know how they can live with the Hippocratic oath," Hall says. Corrective Services says it will work with statistics agency BOCSAR to continually reassess programs, including CUBIT.

Back in jail for the cemetery attack on the young man, Thorne completed for a second time the program he had earlier manipulated, presenting as a "proactive" participant. But having become mired in drugs once more after his 2012 release, he told a counsellor he had thought of committing a sexual assault on another man. Parole revoked, Thorne was sent back to prison. He rejoined society on supervision orders updated last March – treated twice, his rehabilitation unclear.