A man who killed seven pensioners more than 20 years ago won an appeal yesterday to have his murder convictions reduced to manslaughter.

Kenneth Erskine, known as the Stockwell Strangler, argued that his convictions should be overturned on the ground of diminished responsibility.

The Court of Appeal in London was given new medical evidence that he was suffering from chronic schizophrenia at the time of the killings in South and West London and in Islington, North London.

His lawyers argued that he was suffering from an abnormality of the mind that had substantially diminished his responsibility. The Lord Chief Justice, Lord Judge, allowed the appeal and quashed the murder convictions.

Erskine, 46, also had his minimum 40-year life sentence overturned and replaced with an indefinite hospital order. He will soon be transferred from from his present secure mental unit to a high-security mental hospital, where he will stay for as long as doctors consider him a risk to society.

Erskine can have his case reviewed annually by a mental health tribunal, which makes the final decision on whether he can be released. Before release he would have to be moved from the hospital to a low-security unit and be allowed escorted and unescorted leave.

Whoever is the Justice Secretary at the time will not be able to overrule any decision by the tribunal to release him.

Lord Judge said: “This is a straightforward case. It is overwhelmingly clear that, at the time when the appellant appeared at trial, there was unequivocal contemporaneous evidence that his mental responsibility for his actions at the time of the killing was substantially impaired.”

Erskine was 24 when he was sentenced in January 1988 for strangling seven male and female victims, aged between 67 and 94, in their homes in 1986.

Andrew Horne, a consultant psychiatrist at Broadmoor top-security mental hospital, told the Court of Appeal that Erskine’s psychological problems meant that he had been unfit to give evidence effectively enough to participate in his trial.

Symptoms of the illness had been recorded as far back as 1980, when Erskine was 16. While in custody on remand before the trial he had claimed that he could read people’s minds and that he heard the constant screaming voice of a woman being killed.

Dr Horne told the court during a recent hearing: “It was a devastating illness. I think it was as severe as I have ever seen and the impact of such an illness is enormous.”

His victims were Eileen Emms, 78, Janet Cockett, 67, Valentine Gleim, 84, Zbigniew Strabawa, 94, William Downes, 74, William Carmen, 84, and Florence Tisdall, 83. Most of them had been sexually assaulted.

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