The Big Question: Will the new mental health Bill make Britain a safer place?

Why are we asking this now?

The House of Lords began detailed consideration yesterday of the Mental Health Bill, published in November, which would introduce tough new laws to control mentally ill people.

The Bill was proposed eight years ago by the former health secretary Frank Dobson, after the case of Michael Stone, a drug addict suffering from paranoid schizophrenia, who murdered Lin Russell and her daughter Megan, 6, and severely injured Megan's sister, Josie, 9, on a country lane in Kent in 1996 after it was suggested doctors had discharged him because he was "untreatable".

That turned out to be untrue. An inquiry into the case published last September concluded that Stone had not been "deprived of any service that would have made him less of a danger to the public".

Has the Bill been welcomed?

No. It has been much slimmed down after two draft versions were savaged by critics. But opposition to it is undiminished. The Mental Health Alliance, representing 78 organisations including doctors, mental health staff and patients brought together to oppose the Bill, said it was "unfit for the 21st century". Opposition parties have signalled their intention to give it a rough ride through Parliament.

What has so alarmed the critics?

The Bill contains new powers to compel patients discharged from hospital to continue taking their treatment and to lock up people with severe personality disorders judged to be a danger to themselves or others. Doctors and mental health campaigners say these measures are discriminatory, authoritarian and unnecessary. The Royal College of Psychiatrists said compulsion should be used as a last resort and have a "clear clinical purpose."

The Conservativehealth spokesman, Tim Loughton, said: "This Bill is the Government's latest attack on civil liberties. It threatens to extend coercive measures to a wider range of people with the likely consequence that some people with mental illness will be fearful of presenting themselves for treatment in the first place and deteriorate under the clinical radar."

How many patients will be affected?

Louis Appleby, the mental health czar, said "supervised community treatment orders" compelling people to take their drugs would apply to "a few thousand" patients at any one time. In addition, "every clinician" had patients with severe personality disorder who might be detained under the new powers. He accused critics who said the Bill would lead to an increase in compulsion of "scaremongering."

Does anyone support the Bill?

Yes. Marjorie Wallace, the chief executive of Sane, said: "We recognise the concern about protecting civil liberties of those who might be compelled to receive treatment to protect [themselves] or others. Sane believes one in three of the homicides and serious assaults committed by people with mental illness and many of the suicides could be prevented." Rosie Winterton, the Health minister, said there had to be a balance between the rights of patients and the need to protect the public.

Have the changes proposed been tried in other countries?

Yes. There is concern across the world about so called "revolving-door patients" - mentally ill patients who do well in hospital but stop taking their drugs after being discharged, relapse and have to be readmitted. Under the proposed Community Treatment Order (CTO), a patient would be compelled to take their treatment after discharge on threat of being readmitted to hospital.

CTOs are used in New Zealand, Australia and 38 states in the US, where they have provoked controversy. A US study published in 2005 on the Cochrane Database concluded it would take 85 CTOs to prevent one readmission and 238 to prevent one arrest. It is hard to imagine another group where so many people have their liberty curtailed to avoid a single hospital admission or arrest.

Is the Government in breach of its own commitments?

Yes. In 2005, the Department of Health endorsed the Helsinki Declaration and Action Plan for Mental Health which commits ministers to "recognising the need for comprehensive evidence-based mental health policies" (para 8, page 3 of the Declaration). There is no clear evidence to support the view that CTOs are either effective or cost effective. The best evidence shows that intensive, high-quality treatment and care reduces the risk of harm to others.

Why focus on severe personality disorders?

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. The new Bill says all that is required is that "appropriate treatment" should be available. Psychiatrists object to this because they say it turns them into jailers. Their job is to treat the mad, people who might get better with treatment (or at least stop getting worse), not to lock up the bad, which should be a job for the police. The argument centres on people with severe dangerous personality disorders because there is dispute over whether they are mad or bad.

Do inquiries into killings by mentally ill people support the reforms?

No. On the day before the Government published the Bill last November, the report into the killing of Denis Finegan, 50, who was stabbed on his morning bicycle ride through Richmond Park in 2004 in an unprovoked attack by mental patient John Barrett, was published. It said Barrett was "inadequately treated", but the remedy for what went wrong "lies not in new laws or policy changes" but in "sound clinical practice and organisational management."

Paul Corry, of the mental health charity Rethink, said: "Everybody knows the mental health services in this country are not what they should be. If you add human error to that you will get tragedies occurring.

"The answer is not new legislation which diverts time, effort and resources - it is to use the resources to improve the services that we have."

Will the move to control and detain more mental patients protect society?

Yes...

* It will ensure mental patients continue to take their drugs after discharge from hospital, preventing relapse

* It will mean patients with dangerous severe personality disorders can be detained in hospital

* It will prevent the most seriously mentally disordered from slipping through the treatment net

No...

* There is no evidence from other countries that compelling discharged patients to take their drugs works

* Detaining people who have committed no crime and are unlikely to benefit from treatment infringes their civil liberties

* Violence by mentally ill people is rare, hard to predict and can best be reduced by providing intensive high-quality care