On Monday, the HM Crown Prosecution Inspectorate (HMCPSI) released a report on the CPS’s actions in the case of Valdo Calocane.

In June last year, Calocane killed students Grace O’Malley-Kumar, Barnaby Webber and school caretaker Ian Coates, and attempted to kill three other people, in a rampage of terrible violence in Nottingham.

No reasonable jury could conceivably have convicted him of murder

The report was commissioned by the Attorney General, Victoria Prentis, after the CPS was criticised for accepting Calocane’s guilty plea for manslaughter, on the basis of diminished responsibility. As a result of the plea, Calocane was sentenced to indefinite detention in a psychiatric hospital. He will be released, if at all, only when both his treating psychiatrists and the Ministry of Justice say he can be let go. The Attorney General also referred the sentence to the Court of Appeal on the grounds that it is unduly lenient.

HMCPSI has often shown itself willing to be severely critical of the CPS. But this report was, overall, complimentary of the way the service had handled a particularly dreadful and emotive case.

The families of the bereaved as well as many disinterested observers felt at the time that the decision to accept his pleas to diminished responsibility manslaughter meant that Calocane ‘got away with murder.’ Some family members also felt that the CPS had not listened to their concerns and had not communicated with them properly. That view was not shared by every close relative: Ian Coates’s partner told the inspectors that ‘she had no concerns about the CPS’s engagement with her and was complimentary about the service she had received.’

On the main issue of dropping the murder charges, the Report could not be clearer. The CPS made the correct decision:

‘To have continued with an evidentially weak case in the hope that a jury would have been willing to convict because of the horrific nature of the offender’s crimes, would have been wrong and not in accordance with the Code for Crown Prosecutors. The CPS and prosecution counsel considered the relevant law as to the acceptance of the pleas and applied it correctly.’

Two forensic psychiatrists were instructed by the defence, and one by the prosecution. One thought that Calocane was in fact legally insane – a finding which, if accepted by the jury, would have led to his acquittal on the grounds of insanity. But all three agreed that at the very least responsibility for his actions was substantially diminished by his mental illness, a paranoid schizophrenia characterised by hallucinations and delusions, including ‘command hallucinations and delusions of control by an outside force.’ The diagnosis of severe mental illness was not just informed by examination of Calocane in custody, or by the terrible facts of the killings themselves, but also by evidence of his previous involvement with mental health services, and even by downloads on his mobile phone.

Given the broad agreement between the psychiatrists, a trial could realistically have had only two possible outcomes. Calocane could have been convicted of manslaughter on the grounds of diminished responsibility, as well as three attempted murders (to which his diminished responsibility provided no defence). Or, albeit far less probably, the jury could have accepted the evidence of one of the psychiatrists and acquitted him on all charges, including the three attempted murders, on the grounds of insanity. No reasonable jury could conceivably have convicted him of murder.

The psychiatric reports were obtained well in advance of the trial and discussed with Grace and Barnaby’s families. At their suggestion the CPS was persuaded to obtain a fourth report from a psychiatrist who reviewed the other psychiatrists’ reports. He also considered a list of concerns about the psychiatric evidence provided by the families.

The fourth psychiatrist agreed with the conclusions of the other three. This was not even a case where the considerations were ‘finely balanced’. On the contrary his view was that mental illness provided a ‘very compelling dominant explanation’ for the killings.

Only after receiving this report did the CPS make a final decision to accept the pleas to manslaughter.

It was a decision driven – as it should have been – by the evidence and the law. The CPS went against the views of the bereaved, or at any rate most of them, but it was right to do so. If the evidence does not support a charge the CPS should not charge it.

Some mistakes were made. For example, there was no record of Mr Coates’s sons being invited to at least one of the meetings where the psychiatric reports were discussed. Clearly they should have been. And the CPS ought not to have said that their acceptance of pleas followed a ‘consultation’ with the bereaved, because that decision was taken, against their wishes, on purely evidential grounds.

On the issue on which it was asked to report, the Inspectorate’s findings are unsurprising.

Having produced a report on the CPS actions, the Inspectors strayed beyond the Attorney General’s terms of reference and made a series of tentative recommendations about possible reform of murder laws. In particular they referred to a 2006 Law Commission recommendation that some types of manslaughter, including diminished responsibility, should be reclassified as ‘second degree murder’, and asked rhetorically, and confusingly, whether ‘the culpability of the person who commits murder should be reduced to manslaughter by reason of diminished responsibility.’

I’m not sure that this unsolicited advice – which in fairness takes up only a small part of the report –  was particularly wise or helpful. Rather like reform of the House of Lords, that the law of murder should be reformed is one of those things everyone agrees on, until any particular reform is suggested. So it has proved with most of the Law Commission’s 2006 recommendations.

An attempt was made by death penalty retentionists in the 1957 Homicide Act to draw a distinction between capital and non-capital murders. It was not a success, producing absurd anomalies. You could, for example be hanged for a murder committed during a theft, but not for a murder committed during the rape of a child.

The same Act introduced the concept of diminished responsibility, borrowed from Scots criminal law, to ensure that those who killed while under the influence of serious mental illness falling short of legal insanity should not be treated by the criminal law as if they are of sound mind. On the whole it has worked well in England and Wales, as it had in Scotland. The principle holds good whether the person has killed one person or a hundred. Those who kill whilst in the throes of psychotic episodes, confused by hallucinations or manipulated by malevolent voices should not be treated as murderers.