A ROYAL Marine who fatally shot an injured Taliban fighter in Afghanistan could be freed from prison in Wiltshire within weeks.

Sergeant Alexander Blackman, 42, from Taunton was sentenced to seven years on Tuesday for diminished responsibility manslaughter following the recent quashing of his murder conviction.

As a result of time already served since his original conviction in November 2013, the decision of five judges at the Court Martial Appeal Court means it is likely Blackman could be freed next month.

He has already spent almost three-and-a-half years in Erlestoke Prison, near Devizes.

Announcing the seven-year term, the panel of judges, headed by Lord Chief Justice Lord Thomas, said: "As with any person sentenced to a determinate term, his release will ordinarily be at the halfway point of the sentence."

At a hearing last week the judges heard that Blackman's legal team had calculated he would have served the equivalent of a seven-year determinate sentence by April 24.

Blackman watched the proceedings via video-link from prison.

After the judges left court, there was uproar in the public gallery with a huge outburst of cheering and clapping.

Many veterans gave the thumbs-up to Blackman.

One of Blackman's legal team indicated he would probably be released in about two weeks, but the decision on the exact date was for the Prison Service to determine.

The Court Martial Appeal Court ruled previously that 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.

Blackman became the first British serviceman convicted of murder on a foreign battlefield since the Second World War.

But the appeal 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 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".

Blackman was convicted of murder in November 2013 by a court martial in Bulford and was 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.

Blackman shot the insurgent, 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.''

The shooting was captured on a camera mounted on the helmet of another Royal Marine.

During his trial, 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.

Timeline of events

2011

:: March - Sgt Blackman deploys to Helmand province with 42 Commando as part of Op Herrick XIV. His unit is sent to Nad-e Ali, where it sees heavy fighting. Several marines are killed, including Sgt Blackman's troop commander, and others are maimed.

:: September 15 - Taliban insurgents attack a small British patrol base. The attack is repelled with the aid of a British Apache helicopter gunship. Sgt Blackman and his marines are on patrol and sent to look for the fleeing attackers. They find one, lying gravely wounded, in the middle of a field. Sgt Blackman shoots him in the chest with his pistol. The killing is captured on helmet camera by one of the patrol.

2012

:: September - The video of the incident is found on a Royal Marine's laptop during an investigation by civilian police into another alleged crime. A police investigation begins.

:: October 11 - Seven unnamed Royal Marines are arrested on suspicion of murder.

2013

:: October 23 - Sgt Blackman and two others go on trial at the Court Martial Centre in Bulford, Wiltshire, accused of murder. He is only identified as Marine A and his comrades as Marines B and C. They give evidence from behind screens. All three plead not guilty.

:: November 8 - Sgt Blackman is found guilty of murder. The two other marines are acquitted.

:: December 5 - A court rules Sgt Blackman, still only known to the world as Marine A, should be stripped of his anonymity.

:: December 6 - Sgt Blackman, from Taunton, is given a life sentence and told he must serve a minimum of 10 years in a civilian prison.

2014

:: May 22 - Sgt Blackman loses a Court of Appeal bid to overturn his life sentence. His minimum term is cut from 10 years to eight.

2015

:: September - A high-profile campaign begins to have Sgt Blackman freed, led by his wife Claire.

:: December 16 - 1,100 pages of new evidence are handed into the Criminal Cases Review Commission in an attempt to have the conviction sent back to the Court of Appeal.

2016

:: December - The CCRC concludes there is a "real possibility" of overturning the conviction, and grants an appeal. Later the same month, the Lord Chief Justice refuses a bid to grant bail, after prosecutors challenge new psychiatric evidence about his mental state at the time of the killing.

:: December 21 - Sgt Blackman loses a bid to be released on bail in time for Christmas ahead of his appeal hearing.

2017

:: February 7 - Five judges, Lord Chief Justice Lord Thomas, Sir Brian Leveson, Lady Justice Hallett, Mr Justice Openshaw and Mr Justice Sweeney, begin hearing an appeal brought by Sgt Blackman to overturn his murder conviction at the Court Martial Appeal Court in London.

:: March 13 - The Court Martial Appeal Court announces the appeal ruling will be given on March 15.

:: March 15 - Sgt Blackman has his murder conviction replaced with manslaughter on the grounds of diminished responsibility by the court.

:: March 24 - Five judges at the Court Martial Appeal Court hear submissions in mitigation before retiring to consider the sentence, announcing it will be delivered on March 28.