The study says killings such as that by schizophrenic Richard King are rare
The number of killings by people with mental health problems in England and Wales has fallen by two-thirds in the last 30 years, a study has found.
Writing in the British Journal of Psychiatry, researchers say the fall is probably due to improvements in psychiatric care.
The rate of murders has been at an "historic low" since 2000, they added.
Campaigners said the figures showed the common perception there was a high risk of this kind of crime was wrong.
The researchers, from Australia and the UK, looked at official homicide statistics - which cover both murder and manslaughter - in England and Wales between 1946 and 2004.
Analysis revealed that the rate of total homicide and the rate of homicide due to mental disorder rose steadily until the mid-1970s.
The highest annual rate of murders by people with mental health problems peaked in the mid-1970s. In 1973, the rate stood at 0.235 per 100,000 population.
However, by this decade, the rate had fallen significantly. The rate has been at an historic low of 0.07 per 100,000 population, or lower, since 2000.
Care in the community
The team, led by Dr Matthew Large, who is in private practice in Sydney, Australia, said the fall was probably due to better mental health care.
Writing in the journal, they said: "The introduction and increasing use of antipsychotic medication, the greater awareness of the treatment of psychosis by primary care providers after deinstitutionalisation, and the creation of regional health authorities with responsibility for defined populations, may have all contributed to the observed decline in homicide since the 1970s. "
Mental health charities agreed with the conclusion.
A spokesman for the Sainsbury Centre for Mental Health said: "These findings ring true for us.
"Community based mental health services have improved very considerably over the last 20-30 years.
"That's shown by the fact there was virtually no care for people with severe and enduring mental health problems outside hospital, whereas now there are community mental health teams, outreach work and crisis teams to provide support and help."
And the charity Mind said the study showed the perception of the risk of murder and manslaughter by someone with a mental health problem was far worse than the reality.
Alison Cobb, a policy officer with the charity, said: "The number of homicides committed by people with mental distress have long been a tiny fraction of the total, but due to sensational media coverage of one-off cases, there has been a widespread misconception that they are more common than they really are.
"Evidence shows that people with mental health problems are in fact far more likely to be the victims of violent crime than the perpetrators."
But Michael Howlett, director of the Zito Trust, said there were still around 70 homicides each year carried out by people who had had recent contact with mental health services.
He added: "It's good news if the number is coming down, but I would have strong reservations about the way statistics are collected."
Mr Howlett said the official statistics the study was based on would not cover people with personality disorders.