Ethel Quayle and Max Taylor: Locking them up and throwing away the key isn't the answer

Roy Whiting's crime was vile. Here's what we must do to stop others

The death of Sarah Payne brought to the fore concerns about adult sexual interest in children and how we can better protect them. It also raised more specific concerns about the adequacy of the judicial and penal system in dealing with people who pose an extreme danger to minors. Roy Whiting was a known sex offender against children and to that extent, his repeat offence is a terrible lesson.

But framing a fair and effective policy is complicated by the unpalatable fact there are many people whose sexual orientation is toward children, but who do not commit a sexual offence. Sex offenders against children are a very heterogeneous group, with differing personal characteristics, life experiences, criminal history and reasons for offending. That is why it is so difficult to find a single way of dealing with the problem. As far as we know, there is no single psychological "profile" that accurately accounts for all child molesters.

For most adults with a sexual interest in children, their interests and behaviour tend to remain at the level of fantasy. One of the lessons we have learnt in conducting the COPINE studies – investigating the use of pornography on the internet – is that very many people engage in sexual fantasies about children. If the internet is the measure of a "market" in child pornography, consider that one US commercial website showing children involved in sexual acts recorded millions of hits and reaped $1.4m (£960,000) before it was closed down. The signs are that thousands of people are engaging in "abuse at a distance". The growth of that activity may well set the scene for a worrying "normalisation" of sexual interest in children.

Thankfully, the offender who kills a child is very rare. We know, however, that the barriers that hinder people changing from one kind of offender to another can change over time, depending on an array of factors related to opportunity, the extent and nature of deviant ways of thinking, emotional state and whether they are engaged with a community that validates and normalises adult sexual interest in children.

However understandable the revulsion we all felt at Sarah's death, it needs to be put into context. It isn't enough to focus on the "sick" or "deviant" desires of offenders or potential offenders. We need to look at the context in which they live and whether we are doing as much as we could to ensure that people who are at risk of offending are able to live in a way that diminishes, rather than enhances the likelihood that they will act out a particular desire.

What distinguishes Whiting from the vast majority of other paedophiles is that he also murdered a child as part of a sexual assault. Unfortunately, the best predictor of reoffending is a past history of committing such offences. So what went wrong in the handling of Whiting's case? He was classified as "high risk" and not "paedophile" because his assessors did not consider his primary sexual interest to be children. We need to look again at how these classifications are made.

The assessment of dangerousness in sex offenders against children will never be perfect, but it does need continual review. At the same time, we need to remember that risk levels of an offender can change and that individuals cannot fairly be assessed and punished on the basis of a group average for reoffending. Policies should allow for the reintegration of offenders into society, and not assume that all those who commit offences are indefinitely at a high risk of reoffending. If we go down that road, we remove any incentive to offenders to change their behaviour.

Efforts are made in prison and in the probation system to offer offenders opportunity to engage in treatment programmes. Whiting appears to have been offered a place on one such scheme, but refused to attend. This raises the question of what should happen if someone is coming to the end of a prison sentence and is assessed as still dangerous. As things stand, they cannot be further detained, but once released into the community, there is very little control over their behaviour.

The current situation offers only a black and white distinction – in prison or in the community. Terms of release do not take into account whether the offender has made efforts to change behaviour or not. If behaviour has not changed, we put them back into the community where social service support is already overstretched. Proposals to make release contingent on the offender making progress at rehabilitation address half the problem. But what then?

Experience suggests that for many offenders the level of sexual interest in children will never change. The goals of therapy are therefore to provide offenders with the skills to regulate their feelings, and engage in more appropriate behaviour. Another difficulty is that when an individual has participated in such a programme, its effects can only be assessed when they are out of prison, where there are opportunities to reoffend. The sex offenders register offers police the opportunity to monitor and exercise some supervision over offenders, but that is no substitute for more effective monitoring and surveillance. For this reason we believe that the emphasis in the tabloid press on access to the register is partial and overstated.

Many people feel that offenders should be imprisoned because they may pose a risk. Such a policy would mean that people who would not necessarily reoffend remain in prison, because we lack the capacity to make adequate discrimination between offenders.

Sarah Payne's death will undoubtedly harden attitudes towards those who commit sexual assaults on children, and will force a reassessment of the balance between protection of society and protection of children. If protection of children is our only priority, then there seems little alternative to prolonged and sometimes permanent incarceration for most offenders. But surely we want to give people the opportunity to change and the motivation to do so.

We also need to think about new strategies. We have not really explored early-intervention techniques with those who regard themselves as potential offenders. One area of particular concern is the number of adolescents who collect child pornography, a pastime made more accessible by the proliferation of the internet.

One thing that comes across from talking to offenders is a sense of hopelessness. They live with a desperate tension between who they are and who they are allowed to be. Of course, society has a strong duty of care towards children, but we can't neglect the broader context. Offenders are portrayed as scum and scapegoats while "normal" people collude in actively sexualising children – in advertising, popular imagery and fashion. The broader social responsibility cannot simply be off-loaded on to professionals when something goes wrong or channelled into screaming abuse at offenders.

Dr Ethel Quayle and Professor Max Taylor run the COPINE Project at University College, Cork, on the use of child pornography on the internet