What do the Canadians have to say about it? I mention the Canadians only because increasingly they seem to be running their affairs better than any country in the world. They're certainly miles ahead of us on how to run and regulate a banking system; they also appear to take violence against women and sex crimes a lot more seriously than we do. They even have policies about it.

Here's what their department of public safety and emergency has to say about such crimes on its website: "More than most crimes, sex crimes create fear and anger in society. Unfortunately, media stories about sex crimes don't always tell the whole story about treatment and rehabilitation of sex offenders. Research shows that most sex offenders are never convicted again for a sexual offence after serving their sentence and receiving treatment."

So when the justice minister Dermot Ahern said last week that he wasn't in a position to keep rapist Larry Murphy in prison for the entirety of his 15-year sentence, he was telling the truth but avoiding a debate the Canadians have put to bed years ago. He might not have been able to prevent Larry Murphy from leaving prison almost five years early, but he is most certainly in a position to make sure that the next brutal rapist serves out his full sentence.

Treatment is the key. It works and should be a vastly more comprehensive part of the Irish prison system than it is currently. For that reason, it should be a mandatory part of any prisoner's sentence. If he takes part and takes it seriously, he qualifies for the kind of remission enjoyed by Larry Murphy. If he doesn't, he serves his full sentence. Murphy, as we know, had no interest in taking part in the limited treatment available to him in Arbour Hill. It is clearly an insult to justice and to common sense that he should benefit from the blanket remission awarded to most incarcerated people. The law should be changed, therefore, to make it more difficult for sex offenders to enjoy early release.

Some might argue that this discriminates against particular individuals within the prison system, singling them out as special category inmates. But that, of course, is the point. They are different. Most murderers (serial killers aside) are not inclined to kill again once they are released. Their crime was spontaneous and opportunistic, directed against one person on a once-off basis. Put crudely, they got a particular problem out of the way and have no need for further violence.

Without treatment, sex offenders will most likely offend again, and it would appear axiomatic that any jurisdiction that detains them for a long period has an obligation to make sure that the chances of reoffence are minimised. The Canadians have worked this out and have a system where intense work in prison is bolstered by follow-up maintenance programmes after the prisoner has been released.

Research has shown that prisoners who have received treatment are far less likely to rape or commit sexual assault than those who have not.

In Ireland, prison has traditionally been a place of punishment only, somewhere to put what showboating crime correspondents call "scumbags" to get them off the streets. What happens when they get back onto the streets has been of little consequence as far as Irish penal policy goes. That is why we have prisons which have become breeding grounds for criminality, from which people emerge more hardened than when they went in. It's why somebody like Larry Murphy can earn remission for "good behaviour" even when that behaviour involves a refusal both to grapple with the enormity of what he has done and to receive treatment that would reduce the risk that he would do it again.

Criticism of Dermot Ahern for not keeping Larry Murphy in prison is, with no due respect to the people making it, stupid and ignorant. Murphy's been in prison for more than 10 years, Ahern in the Department for Justice for just two; legislation shouldn't be made retrospectively to target one person the showboaters have decided is the personification of all evil. Ahern will deserve criticism, however, if he ignores the obvious anomaly that has been highlighted by Murphy's release. His term in Justice has so far been marked by well-hyped laws that have little practical effect. He now has a chance to make one small change to the law, which would have hugely positive consequences, not least for the safety of Irish women, whose concerns seemed to pale into insignificance last week compared to the need to play "gotcha" with one released prisoner.

Ivor great idea: election would get rid of Callely

All sorts of suggestions have been put forward over the last few weeks about how to remove Ivor Callely from the Seanad. They range from the unprintable, to the ones that are probably illegal under incitement-to-hatred legislation to convoluted constitutional changes that would make it easier for Brian Cowen to rid himself of his infernal senator. It doesn't have to be so complicated. There is one easy way to get rid of Senator Callely, which is what Cowen has been hinting he wants. That way is to call a general election. Once the Dáil is dissolved, the Senate quickly follows, and Callely returns to life as a private citizen. We'd lose Cowen as well, of course, although I have a sneaking suspicion most people could live with that.

ddoyle@tribune.ie