Royal Marine Alex Blackman's sentence has been reduced to seven years, meaning he will soon be free
Five judges at the Court Martial Appeal Court are to sentence Sergeant Alexander Blackman, 42, from Taunton in Somerset, following their recent decision to reduce his murder conviction to diminished responsibility manslaughter.
They heard moving mitigation on his behalf at a hearing in London last week, including a plea for "exceptional mercy" to be shown to enable his immediate release from jail.
Jonathan Goldberg QC told the panel of judges, headed by Lord Chief Justice Lord Thomas, that Sgt Blackman was the "last casualty of a failed war".
He has already served almost three-and-a-half years since his conviction, which Mr Goldberg said equated to a "determinate sentence of almost seven full years".
The Court Martial Appeal Court has ruled previously Sgt Blackman was suffering from an "abnormality of mental functioning" at the time of the 2011 killing in Helmand province when he was serving with Plymouth-based 42 Commando.
The court found the incident was not a "cold-blooded execution" as a court martial had earlier concluded, but the result of a mental illness, an "adjustment disorder".
The judges said Sgt Blackman had been "an exemplary soldier before his deployment to Afghanistan in March 2011", but had "suffered from quite exceptional stressors" during that deployment.
They found his ability to "form a rational judgment" was "substantially impaired".
Sgt Blackman was convicted of murder in November 2013 by a court martial in Bulford, Wiltshire, and sentenced to life with a minimum term of 10 years.
That term was later reduced to eight years on appeal because of the combat stress disorder he was suffering from at the time of the killing.
Sgt Blackman shot the fighter, 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.
He told him: "There you are. Shuffle off this mortal coil, you c***. It's nothing you wouldn't do to us."
He then turned to comrades and said: "Obviously this doesn't go anywhere, fellas. I just broke the Geneva Convention."
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The shooting was captured on a camera mounted on the helmet of another Royal Marine.
During his trial, Sgt Blackman, who denied murder and was known at that stage as Marine A, said he believed the victim was already dead and he was taking out his anger on a corpse.