The Court Martial Appeal Court’s judgment which ruled that Alexander Blackman (Marine A) was guilty of voluntary manslaughter, not murder, has prompted both jubilation and horror in equal measure. One interesting aspect of the judgment is the Court’s conclusion that it could consider the defence of diminished responsibility at all. To reach it, the Judges had to sidestep recent case law which was very much against the appellant.

Blackman’s crime was to fatally shoot a Taliban insurgent in Afghanistan’s Helmand province. Had the shooting been in the heat of battle no one would have questioned its legality, but this was not the case – the victim was unarmed and severely injured already. Most importantly, the victim had been taken prisoner and so was entitled to the rights accorded to such persons by international law. Mr Blackman’s injunction to his colleagues to keep the incident secret because he had “broken the Geneva Convention” was a key feature of the case.

Blackman’s supporters argue that he himself is a victim, either because of the immense pressures he was placed under by his superiors, or because the person he killed was an enemy combatant. Others, including the jury, felt that his actions were cold-blooded murder.

Before examining the legal significance of Blackman’s case, it must be recognised that the Court Martial Appeal Court’s latest ruling in the case did not exonerate the marine. Blackman admitted voluntary manslaughter – an extremely serious crime for which the maximum penalty is life imprisonment. His appeal was based on a special defence of diminished responsibility, not on arguing that the killing was justified.

In order to even consider whether diminished responsibility applied, the Court had to be satisfied that there was a good reason for the defence not having been raised at trial. The court stated, at paragraph 69:

“Critical to our conclusion on this issue is that, at the initial hearings before this court in December 2016, the prosecution accepted that there was a reasonable explanation for the failure to call psychiatric evidence at trial and, thus, for failing to advance the partial defence of diminished responsibility. This concession has meant that it is not right to conclude that there was a tactical reason for failing to deploy it. Had it been otherwise, it would not have been appropriate for this court to consider the defence at all: see R v Erskine [2009] EWCA Crim 1425, [2010] 1 WLR 183.”

This is an unusual approach. The Court appears to say that, but for the prosecution decision, the appeal would have been doomed to failure.

Other than the concession, the Court’s only other reasons that the defence should have been considered are of little weight. The fact that Mr Blackman did not want to raise a “psychological defence” because of “stigma, perception of weakness and the likely end of his career”[1] could apply to almost any defendant and are of little relevance. Indeed, they suggest not so much a good reason for not raising the defence (which would weigh in favour of admission), but a deliberate and informed decision not to – which ultimately mitigates against it[2]. Equally, the fact that the only psychiatric evidence available at Mr Blackman’s trial was minimal and irrelevant to the question, only serves to highlight the failure of his original defence team (not representing him on appeal) to properly investigate the defence of diminished responsibility.

Ultimately, as the Court stated, the prosecution’s concession was the critical issue in deciding whether the evidence founding the defence of diminished responsibility was admitted. Its admission was, of course, determinative of the appeal.

The Court’s reliance on the prosecution’s concession (for which it cited no authority) allowed it to distinguish the case of R v Erskine [2009] EWCA Crim 1425. There, the Court gave guidance on when fresh-evidence founding a defence of diminished responsibility should be considered on appeal. That guidance, unsurprisingly, heavily restricts the admission of such evidence. The judgment makes clear that there must be a “reasonable and persuasive”[3] explanation of why a defence and/or evidence was not raised at trial before they are admitted on appeal. The Court went on to state that the parties must provide a detailed analysis examining, among other things, what evidence was available at trial and why the evidence had not been provided to the court of first instance. As outlined above, the evidence in Mr Blackman’s case didn’t even come close to providing a good reason for the defence not being run.

On one view, the approach of the Court Martial Appeal Court could be seen as a decision not to go behind dealings between the parties to a case where the question involved tactics at trial. On the other, it is hardly appropriate for a determinative issue in a murder case to be decided without reference to the Court. Taking such an approach is in effect delegating part of the powers of the Court to the prosecution.

Overall, it is hard to avoid the conclusion that the Court Martial Appeal Court was particularly sympathetic to Mr Blackman. It is possible that the unorthodox approach to the admission of fresh evidence arose from a desire not to dismiss Blackman’s case on what might have been seen as a technicality. A less high profile case may have received very different treatment.

The fact that the decision rests on a concession by the prosecution, severely curtails its usefulness for future appellants seeking to raise diminished responsibility for the first time on appeal. It is easy to imagine a future Court Martial Appeal Court dismissing a case where no prosecutorial concession had been given. Erskine remains the relevant authority in such situations.

Conversely, it is unclear what impact the Court’s approach will have on other fresh evidence cases. Will prosecutors be much less willing to concede that there was a good reason for evidence not being admitted at trial? It seems at least possible.

Given the continued involvement of British personnel in armed conflict and the increasing prevalence of video recording in war-zones, it is inevitable that cases of this type will continue to come before the courts. However, it remains to be seen whether the Court Martial Appeal Court will extend to future defendants the same remarkable sympathy that it has to Mr Blackman.