The Big Question: Should the severely disordered be locked up to protect the public?

Why are we asking this now?

Michael Stone, a drug addict with a severe personality disorder, is serving three life sentences in Wakefield prison for the murders of Lin Russell and her daughter Megan, six, as they walked down a country lane in Kent in 1996. Megan's sister, Josie, aged nine at the time of the attack, was severely injured and left for dead, but survived. An inquiry into the care of Stone, then aged 37, published yesterday, identified a catalogue of failures by the mental health, addiction and prison services over five years from 1992 to 1997, when he was arrested and charged. He had been in trouble with the law since his first conviction at the age of 14. The report was completed in 2000, but publication was delayed for legal reasons.

Does the report show the murders could have been avoided?

No. There were many failings in the care Stone received, but even if they had all been remedied the inquiry found there is no guarantee that things would have turned out differently. The 384-page document said there was no suggestion that Stone "was deprived of any service which would have made him less of a danger to the public". It added: "This is emphatically not a case of a man with a dangerous personality disorder being generally ignored by agencies or left at large without supervision."

Can the public be protected from people like Stone?

People with severe personality disorder present the toughest challenge to the mental health services. Many features of the Stone case are depressingly familiar from previous scandals, back to the killing of Jonathan Zito by Christopher Clunis in 1992, and subsequent cases such as that of Daniel Gonzalez, jailed for life in March this year, after he went on a killing spree which left four people dead. Robert Francis QC, the inquiry chairman, said there were "policy implications" of the inquiry's findings, but these were beyond its remit, which was to look solely at the care and treatment of Stone. The Government, however, decided soon after Stone was convicted that the answer was to change the law. Jack Straw, then Home Secretary, was outraged by the response of psychiatrists who protested that Stone was "bad, not mad", and that the task of coping with him should have fallen to the criminal justice system. In December 2000, spurred on by the public outcry over the case, the Government launched a White Paper, Reform of the Mental Health Act, which proposed the biggest overhaul of mental health legislation for 40 years. Public confidence had been undermined, it said, by the failure to provide "adequate public protection from those whose risk to others arises from a severe personality disorder. We are determined to remedy this."

What is wrong with the law?

The 1959 Mental Health Act (updated in 1983) specifies that patients may only be detained against their will if they pose a risk to themselves or others and "treatment is likely to alleviate or prevent deterioration of their condition" - the so-called treatability test. The Government said this was too narrow a definition because it meant any patient who failed to respond to treatment could be discharged - even if they were judged dangerous. Psychiatrists objected that it was their job to treat people who were mad - those with a mental illness - but not to act as jailers of people who were bad.

Can people with severe personality disorder be treated?

This goes to the heart of the problem. Is there a cure for nastiness? There is still disagreement among psychiatrists about what the diagnosis means or to whom it should be applied. These are people, once called psychopaths, who have had abusive childhoods and grown up into unpleasant, aggressive and sometimes dangerous adults. They may not be (mentally) ill in the conventional sense and have been held to be untreatable. But new research has suggested that some may respond to intensive therapy delivered over a long period of time.

How big a risk do they pose?

The most widely repeated myth is that killings by mentally ill people have risen as a result of the policy to care for them in the community. In fact there has been no increase in the 40-plus years that the mental hospitals have been emptying. The murder rate has soared during this time and as a result the proportion of homicides by mentally ill people has declined. The number stands at between 30 and 40 a year - less than 10 per cent of the total of 500 to 600 a year.

Can we spot those likely to kill?

This is a second myth. There are 600,000 people with severe mental illness of whom 1 per cent are judged at risk of harming themselves or others. Most are at risk of suicide. The risk of homicide in a person diagnosed as psychotic is estimated at one in 15,000. No test is sensitive enough and no psychiatrist clever enough to pick up such extremely rare events in every case. A review of inquiries into homicides by mentally ill people concluded the killing was not predictable.

Do mental health organisations support a change in the law?

Far from it - they were appalled at the focus on protecting the public rather than the person suffering from the mental or personality disorder. Two attempts to produce a mental health Bill have foundered in the face of concerted opposition from an alliance of mental health groups, representing psychiatrists, community workers and patients. The Government has now promised a slimmed-down "amending Bill", yet to be published, but which will still extend compulsory detention powers to people with severe personality disorders.

So what should be done?

Better services, properly funded with more effort to intervene early and better communication between all the agencies. This cannot guarantee tragedies like the Stone case will never happen again, but it is the best way of reducing the risk. As Shaun Russell, husband of Lin and father of Josie and Megan, said yesterday: "If everybody had done their job right perhaps [Stone] wouldn't have done what he did."

Does the law need changing to protect us from people like Stone?

Yes...

* People with dangerous severe personality disorder pose a risk to themselves and others

* New research suggests that with intensive therapy they can be treated

* A change in the law would allow such people to be detained in hospital

No...

* It is impossible to identify accurately the small number of mentally ill people who will commit violent offences

* The role of psychiatrists is to treat the mad, not act as jailers of the bad

* The best way to reduce the risk to the public is to improve communication among the caring agencies