Anthony Joseph has been detained indefinitely for killing another man on a night bus in north London in 2005. It is the latest in a series of cases which have highlighted the difficulty of judging if someone has genuine mental health problems. Is there not a better way?
Wayne Royston killed a man in Bargoed, south Wales. Prosecution refused to accept diminished responsibility plea. Jailed for life for murder in Nov 2006
Stuart Harling jailed for life in Jun 2007 for murder of nurse Cheryl Moss. Harling's lawyers claimed he suffered from Asperger's syndrome and a personality disorder
Kemal Dogan given life on 12 Dec 2007. Claimed he was suffering from severe depression when he killed wife Aygul
Anthony Joseph claimed to be schizophrenic. Two trials ended in hung juries. Prosecution finally accepted plea of guilty to manslaughter on grounds of diminished responsibility. Sent to Broadmoor on 20 Dec 2007
Garath Davies convicted of murdering jogger Egeli Rasta despite diminished responsibility defence. Sentenced next month
Stabbing a complete stranger to death for no apparent reason may appear - to the layman - to be the actions of a "madman".
But when it comes to the law there is a fine line between being "mad or bad".
Every year dozens of juries all over the country are asked to decide for themselves - based on often diametrically opposed views from psychiatric experts - if someone is guilty of murder or manslaughter, due to diminished responsibility.
In recent months there have been a number of high-profile trials in which there was little doubt the man in the dock was the killer but he and his legal team were seeking to persuade the jury that a mental disorder had removed his ability to form intent.
The case of Anthony Joseph was one of the hardest to judge.
Joseph's defence counsel, Philip Katz QC, claimed his client was suffering from the onset of schizophrenia when he killed Richard Whelan on a night bus in north London in July 2005.
The prosecution initially refused to accept the diminished responsibility defence. At the retrial Victor Temple, QC, said: "The defendant had been drinking and taking drugs and needed little or no excuse to turn his pent up anger against the innocent victim."
He pointed out Joseph had gone out and bought a knife only hours after being freed from prison.
The defence of diminished responsibility in this case has been used as a defence for the indefensible, with so much evidence showing that Anthony Joseph was an angry and vindictive man
Two psychiatrists gave differing views and two juries were unable to reach verdicts, with the prosecution eventually agreeing to accept the diminished responsibility plea.
Richard's family were angry and his sister, Teresa Ward, said outside court that diminished responsibility was a "defence for the indefensible".
Last week the government announced "the next step in the first comprehensive review of murder law for 50 years".
The Ministry of Justice said it was seeking the views of key "stakeholders" on a report by the Law Commission which suggested, among other things, a reform of the defence of diminished responsibility.
A Ministry of Justice spokeswoman said: "Where mental disorder is cited as a diminished responsibility defence, a successful defence may lead to a hospital order which requires evidence from at least two psychiatrists, one of whom must be registered as having special experience in the diagnosis and treatment of mental disorder."
But in several recent cases psychiatrists have given very different views on the sanity of the defendant.
Kemal Dogan went on trial accused of murdering his wife, Aygul, after he found her exposing herself on a webcam and flirting with another man in an internet cafe near their home in north London.
Dr Tony Nayani, giving evidence for the defence, said Dogan had been suffering from "medium to severe" depression at the time of the killing and had also reported hearing voices and seeing animals talking to him.
But two other psychiatrists disagreed with Dr Nayani's diagnosis.
One of them, Dr Thomas McLintock, told the court that Dogan was possibly "malingering" and may have been "coached by another patient".
He said there were serious inconsistencies in the symptoms Dogan was presenting and he pointed out that the defendant smiled and laughed when he was visited by his family at the John Howard Centre, a forensic mental health unit in east London.
The jury found Dogan guilty of murder and he was jailed for life.
The government has in the past suggested removing juries from complex fraud trials, although it has yet to introduce legislation.
'Jury right forum'
Barristers have opposed the idea of doing away with juries in fraud cases and Sally O'Neill QC, from the Criminal Bar Association, said she was similarly reluctant to remove them in homicide cases.
She said: "Expert evidence is always difficult for juries and when you have expert witnesses disagreeing then it can be very difficult.
"Sometimes the issues can be very complex but juries are usually able to form a view and I still feel the jury is the right forum. It is usually a question of presentation and that is up to the prosecution."
The Ministry of Justice insists it is right for a jury of laymen to be the final arbiters of guilt, rather than a panel of psychiatric experts. A spokeswoman said: "In a criminal trial which relies on a jury to determine issues of guilt and criminal responsibility, the decision has to be informed but not determined by expert opinion.
"As the European Court has noted, psychiatry is not an exact science. Medical evidence on the single issue of a defendant's mental state is likely to vary widely between doctors, and much more so the issue of criminal responsibility, which turns as much on cultural as medical issues.
The law needs to be clear and fair so that people have confidence in the criminal justice system
"The point that juries may find it hard to conclude the issue of responsibility simply reflects its complexity.
"It is not an argument for delegating the decision to expert opinion which will necessarily approach it from a narrower professional perspective, and with no greater prospect of agreement."
Justice Minister Maria Eagle said: "Murder is the most serious crime and it is essential that the law reflects this. "The law needs to be clear and fair so that people have confidence in the criminal justice system. We want to have an open and inclusive debate on the issues before we bring forward firm proposals on how the law should be reformed."
'Not for jurors'
Michael Howlett, director of the Zito Trust, said he would prefer a system whereby the jury simply decided whether a defendant had committed "homicide".
"It would then be left up to the judge to decide based on the evidence - including the psychiatric evidence - what was the most appropriate way of dealing with the person who was convicted. This distinction between murder and manslaughter is way out of date," he said.
Consultant clinical psychologist, Elie Godsi, agrees and believes the current system is "flawed".
Mr Godsi, the author of Violence and Society: Making Sense of Madness and Badness, said: "Psychiatrists' opinions are not objective. It is not like diagnosing cholera or some other illness. The notion that it is clear cut is a myth."
The diminished responsibility plea can be abused in some rare cases, but it usually reflects that a person is not capable of rational action.
Chief executive, Sane
He said it would be better to have a system whereby homicides could be graded to take into account a number of factors, including premeditation, provocation and mental illness.
Mr Godsi also pointed out that those killers who fake mental illness because they see "mad as the soft option" may be mistaken.
"They usually get banged up indefinitely and their time in hospital is proportionate to the crime they committed rather than how ill they are," he said.
Marjorie Wallace, chief executive of the mental health charity Sane, said: "The diminished responsibility plea can be abused in some rare cases, but it usually reflects that a person is not capable of rational action.
"While we recognise the concerns of victim's families and loved ones, Sane believes that the law should be able to demonstrate compassion towards those who commit crimes - however terrible - when the balance of their mind was disturbed."