An independent inquiry is to examine how a paranoid schizophrenic who stabbed to death a police officer was considered safe to be cared for in the community.

Martial arts enthusiast Glaister Earl Butler - detained indefinitely at a high security hospital today after admitting manslaughter due to diminished responsibility - had a history of violence as well as delusions about the police.

He was seen with a knife by his carers just four days before the killing of Detective Constable Michael Swindells (pictured), who was trying to arrest Butler for threatening to decapitate a council carpenter on May 21, last year.

Other mental health workers also expressed concern that Butler refused to accept he was ill and was unwilling to take medication to control his condition since first coming to their attention in 1994.

A mental health charity said the tragic case highlights the "inadequacies" of supervising some patients in the community, and the defendant's brother also said Butler should have been in care and had been "let down" by the system.

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In Friday's Birmingham Post: Why was he allowed to kill?

Why was a paranoid schizophrenic with a history of violence free to stab Pc Michael Swindells to death? An in-depth look at the issues surrounding care in the community plus latest reaction.

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The 49-year-old defendant, from Long Acre, Nechells, was formally cleared of the officer's murder on the direction of a judge at Birmingham Crown Court today.

He had earlier admitted manslaughter due to diminished responsibility.

Mr Justice Calvert-Smith ordered Butler to be detained indefinitely at Ashworth high security hospital in Liverpool and said he could not envisage a time when Butler would not pose a "serious danger" to either himself or the general public, and especially the police.

He also praised the "immense courage" of the 44-year-old officer for tackling an "armed, dangerous and determined man" without protective clothing.

"He joins a large number of police officers who have given their lives as public servants," the judge said.

"The grief of his family, colleagues and the citizens of Birmingham can, and I hope will, be mixed with pride for his selfless devotion to duty that led to his death."

Outside court, consultant psychiatrist Dr Neil Deuchar, the medical director of Birmingham and Solihull Mental Health Trust, said a formal internal review would be undertaken into their care of Butler since 1995.

To them, Butler had appeared to have been taking his medication while if he had appeared to be suffering a relapse, they would have intervened, he told reporters.

He added: "(The Trust) is extremely concerned that a tragedy such as this has occurred. We are extremely keen to understand in great detail the circumstances which led to this incident."

An independent inquiry would also be undertaken by the Birmingham and Black Country Strategic Health Authority, he said.

Dc Swindells's widow, Carole, and his family were said to be "content" with the outcome of the case.

Detective Chief Inspector Glenn Moss, from West Midlands Police said: "They accept that Mr Butler clearly had an illness and needs treatment for that illness."

But Butler's family considered the mental health system had failed him.

His brother, who declined to be named, said: "He has been let down by the system and that's it. He has been ill for more than 10 years. There's nobody done nothing for him.

"He should have been in the care of mental health services at the time."