The murder conviction of Royal Marine Sgt. Alexander Blackman has been overturned by five of the country’s most senior judges sitting in London’s Court Martial Appeal Court. He may be released from prison as early as Friday after serving just three years and four months out of his original 10-year term.

Blackman was found guilty of murdering an injured Afghan prisoner of war by a military court in November 2013 and sentenced to life imprisonment, with a minimum term of 10 years. Blackman’s arrest and that of other marines in his patrol only occurred after video footage was found on a laptop, belonging to a military serviceman, by UK civilian police.

The footage, inadvertently filmed from another marine’s helmet-mounted camera, showed the callous killing of an Afghan fighter on September 15, 2011 in a cornfield in Helmand province, Afghanistan. Blackman was filmed shooting the Afghani in the chest at close range, after he and his patrol found the man seriously injured by gunfire from an Apache helicopter.

After he killed the prisoner, Blackman declared, “There you are. Shuffle off this mortal coil you c***. It’s nothing you wouldn’t do to us.” He then turned to his patrol and told them, “Obviously this doesn’t go anywhere, fellas. I just broke the Geneva Convention.”

The Geneva Convention governs the treatment of captured and wounded prisoners of war, and forbids the mistreatment or summary execution of combatants who have laid down their weapons or are no longer able to fight. Blackman’s act was in blatant violation of international law, something that he himself acknowledged in the video.

In spite of this admission, Blackman, at his initial trial, denied murder, claiming that he believed the insurgent was already dead when he shot him. That this was patently false, however, was provided by expert witness testimony. A pathologist described the physical movements of the prisoner before he was killed and said that in his expert opinion he was still clearly alive.

Blackman, who served five tours in Iraq and Afghanistan, was the first member of the UK armed forces to be convicted of murder since the Second World War. He had previously appealed his life sentence at the Court of Appeal in May 2014 but lost. However, the minimum term was cut from 10 years to eight.

This second appeal comes after years of campaigning by some of the most right-wing elements of the media and by sections of the military. They sought to exonerate Blackman of the charges of war crimes and glorify the UK armed forces in order to prepare the ground for future acts of imperialist violence.

In October 2015, an unprecedented demonstration of former and serving Royal Marines in full uniform took place in London in defence of Blackman, and in defiance of official instructions that forbid the armed forces from attending political protests in uniform. The protest marched through the capital to Downing Street where Blackman’s wife, Claire Blackman, handed in a letter to then Prime Minister David Cameron demanding a review of his case.

The protest was widely supported and promoted by the media, most prominently by right-wing newspapers the Daily Express and the Daily Mail, with the latter starting a “campaign for justice” in support of Blackman. This campaign raised over £800,000 in donations, and provided the finance to launch a new appeal against his conviction.

The campaign also received the support of Sun and Daily Mail columnist Katie Hopkins, who is notorious for her xenophobic and fascistic diatribes in favour of militarism and against refugees, whom she has likened to “cockroaches” and a “plague of feral humans.” After judges overturned Blackman’s conviction, another Daily Mail columnist, Amanda Platell, praised the “courage” and “dignity” of Blackman and lauded the “heroic campaign” for his release, calling for his wife, who had led the campaign, to be given a medal for bravery.

The second appeal was mounted on the basis of new evidence having been found relating to Blackman’s mental state at the time of the murder. Blackman’s legal team argued that the conditions that members of his 42 Commando unit faced in Helmand province were “austere” and a “breeding ground” for mental health problems.

Jonathan Goldberg QC, who led Blackman’s legal team, stated, “Only those who have been on the front line can know what it is really like.” Psychiatrists who gave evidence at the appeal contended that Blackman had been suffering from an “adjustment disorder” which had impaired his ability to make rational decisions and had “numbed his moral compass.”

Accepting these claims, the five appeal court judges ruled that Blackman’s conviction should be reduced from murder to “manslaughter on the ground of diminished responsibility.”

In their ruling, the judges stated that Blackman had suffered from “quite exceptional stressors” which had increasingly impacted on him during his tour in Afghanistan. According to the judges, it was “clear that a consequence was that he had developed a hatred for the Taliban and a desire for revenge.”

Blackman’s acquittal, however, has been opposed by some sections of the armed forces—not out of humanitarian concerns or opposition to the war crime he committed—but because the portrayal of Blackman as mentally unstable could tarnish the reputation of the army.

Speaking to the Telegraph, Major Steve McCulley, who was the commanding officer in charge of Blackman’s unit shortly before the killing, complained that the description of his unit as “gung-ho” and “feral” was a “dagger through the heart” of the Marines.

“So many people are upset [about this description]… I am not just talking for myself, I am talking for a lot of marines right through the ranks who have been in touch with me… It is destroying the memory of those men who paid the ultimate sacrifice.”

This description was part of a defence put forward at the appeal by Colonel Oliver Lee, who was briefly Blackman’s commanding officer, in which he had also stated that Blackman’s unit was “completely out of control” after five months in Afghanistan.

He claimed that marines fighting alongside Blackman were abusive and contemptuous towards Afghan citizens and had little regard for the rules of engagement. Some marines in Helmand province were guilty of dehumanising the enemy, he continued, and it was wrong to treat Blackman as a “single rotten apple.”

Another army figure, Sergeant Rob Driscoll, who was leading a nearby patrol when Blackman shot the Afghan fighter, echoed the comments of McCulley, stating that he and the troops were “disappointed” with the way they had been portrayed.

The comments from figures in the army, and the media push to celebrate the military and gloss over its war crimes, make it clear that any affront to the armed forces that could further discredit the UK’s imperialist operations abroad will not be tolerated by the ruling elite.