Marine’s life sentence is fixed by law – but the minimum term is not so simple | Joshua Rozenberg

In setting Sergeant Blackman’s minimum term for murdering a Taliban prisoner, what principles must the court consider?

Sergeant Alexander Wayne Blackman will be sentenced to life imprisonment on Friday.

Formerly known only as Marine A, Blackman was convicted by a court martial on 8 November of murdering an Afghan prisoner more than two years ago, and the sentence for murder is fixed by law. Blackman was refused permission on Thursday to challenge the lifting of an order that had protected his identity during his trial.

The fact that the wounded insurgent was killed by Blackman in Afghanistan makes no difference to the Royal Marine’s legal position. British troops are bound by the criminal law of England and Wales wherever they serve. Indeed, any British citizen can be convicted in England and Wales of committing murder or manslaughter abroad.

Under section 269 of the Criminal Justice Act 2003, a court must also set the minimum term that a person convicted of murder will serve in custody before being considered for release on licence. Schedule 21 of the act sets out a number of general principles the court must consider.

Setting the minimum term will not be a straightforward task because Blackman was convicted by a court martial, a military court. The principles in the 2003 act have not been considered before in the case of a battlefield murder. And there is a further complication, intrinsic to the UK’s system of military justice: sentencing is not a matter for the judge alone.

A court martial consists of a civilian judge – still called the judge advocate – and a board comprising members of the armed forces, who must be senior in rank to the defendant but not connected to the defendant or the prosecution. Normally the board has five members, but in serious cases such as this one it may have seven. The board decides on the verdict in broadly the same way as a jury – except that it can convict by a simple majority. The defendant has no right to be told that the verdict was not unanimous, even if nearly half the board had supported an acquittal.

After conviction, the judge advocate and the board meet to set the sentence together. This, too, can be decided by a simple majority of the judge and the board, so five members of a seven-person board could outvote the judge. It is only if the board and the judge are split equally that the judge advocate has a casting vote.

In practice, you would expect a board of non-lawyers to pay great heed to the sentencing advice given by a legally qualified judge. If the board goes out on a limb, it can expect its decision to be overturned by the court martial appeal court.

But Blackman’s case could be different. Serving officers in the navy and the marines may have a perspective that is not shared by a judge – even though Judge Blackett, the judge …read more