A Royal Marine found guilty of murdering an injured Afghan fighter has had his sentence reduced.

Sergeant Alexander Blackman, who is believed to have grown up in Brighton, failed to overturn his conviction at the Court of Appeal yesterday.

But three leading judges cut his minimum term from ten to eight years because of the combat stress disorder he was suffering from at the time of the incident.

As well as the imposition of a life sentence Blackman, now 39, was “dismissed with disgrace” from the Royal Marines after he had served with distinction for 15 years, including tours of Iraq, Afghanistan and Northern Ireland.

The killing happened in Helmand province in 2011 while Blackman, who is known as Al, was serving with Plymouth-based 42 Commando.

He shot the Afghan, who had been seriously injured in an attack by an Apache helicopter, in the chest at close range with a 9mm pistol before quoting a phrase from Shakespeare as the man convulsed and died in front of him.

Afterwards he turned to comrades and said: “Obviously this doesn’t go anywhere, fellas. I just broke the Geneva Convention.”

During the trial Blackman was known as Marine A.

Blackman, who denied murder, said he believed the victim was already dead and he was taking out his anger on a corpse.

He has said he felt ashamed at his lack of self-control, describing it as a “stupid lack of self-control and lapse in judgment”.

Reducing the minimum term Lord Thomas said: “His mental welfare had not been assessed in the way in which it would ordinarily be assessed by a commanding officer and there is evidence that he was becoming somewhat paranoiac about the Taliban’s ‘gunning’ for him.”

The judge added: “Taking into account the whole of the evidence we conclude that combat stress arising from the nature of the insurgency in Afghanistan and the particular matters we have identified as affecting him ought to have been accorded greater weight as a mitigating factor.”

An MoD spokesman said after the ruling: “We respect the authority and decision of the appeal court and it would be inappropriate for us to comment on the sentence.”

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