A Royal Marine accused of "encouraging or assisting" another marine to execute a captured Afghan insurgent told a court martial that he had no idea he would shoot him.
The serviceman, known only as Marine C, took to the witness box to answer allegations that he was involved in committing the alleged murder.
Marine C is on trial at the court martial centre in Bulford, Wiltshire, alongside two other servicemen, known only as Marine A and Marine B.
Marine A is alleged to have shot the Afghan national in the chest at close range with a 9mm pistol, while Marine B, like Marine C, is accused of being "party to the killing" and "encouraged and assisted" him.
The men are charged with murdering an unknown captured Afghan national on or about September 15 2011. All three deny the charges.
From the witness box, with his identity protected from behind a screen, Marine C told the board he had no idea that Marine A was going to shoot the insurgent.
Marine C explained that Marine A had told him to join the rest of the patrol, which was some distance away from the injured insurgent.
As he walked away - believing the insurgent to be dead - Marine C said he heard a gunshot, which he knew was from a pistol, so assumed it could only have been Marine A.
Marcus Tregilgas-Davey, representing Marine C, asked: "Had you any idea that was going to happen?
Marine C replied: "No."
The serviceman also confirmed that he had neither said or done anything that could be regarded as "encouraging or assisting" Marine A commit the alleged murder.
The incident had been captured on a camera mounted on the helmet of Marine B, which has been played to the court.
The footage shows the armed insurgent - who had been seriously injured in an attack by a Apache helicopter - being dragged across a field in Helmand Province.
On the footage marines can be heard swearing at the man calling him a "f***ing prick", "f***ing c***" and "bastard".
Marine A was filmed walking forward, bending down and shooting the man in the centre of his chest with a pistol.
The Afghan was seen dying as Marine A looked on, telling 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", it is alleged by prosecutors.
Marine C told the seven-strong board that when he first saw the insurgent he thought he was "very severely" injured and thought he was "likely to die at any moment".
"I was scared," Marine C said.
"I was in the middle of a field in a known hotspot of enemy activity and 50 metres away from the rest of my patrol."
Marine C said that as he was acting at the "cover man" for Marine A, who was checking the insurgent for weapons, he kept his pistol trained on the insurgent and was, in his view, following the correct procedures.
Marine C also said that he thought the insurgent, who is being seen on the video being dragged across the field, was moved correctly by the other marines.
He said that after Marine B had given the Afghan medical treatment and Marine A had told their superiors the man was dead, he was ordered to join the rest of the patrol.
He said that when he left the insurgent Marine A did not have his pistol out and he did not see him remove it from the holster either.
But he did hear the shot and said that he had "assumed" Marine A had shot the insurgent.
"I heard across the radio is 'proper dead now' so I put two and two together and made an assumption," he told the court.
Mr Tregilgas-Davey took Marine C through the video footage, which includes him saying "I'll put one in his head, if you want".
Marine C explained that this was not a serious comment and described it as "banter".
He added: "It was just a spur of the moment comment, a throw away comment to break the ice of the situation.
"Commando humour is to try and make light of a serious, scary, horrible situation... to try and relax everyone."
He said the "maybe we should pump one in his heart" comment was wrong and was again not a serious remark and was not aimed at Marine A.
"Again, it was just a throw away comment, banter," he said.
Marine C said that his comment of "he's dead" was in fact him relaying to other marines Marine A's original remark that the insurgent had died.
"I would have thought he was probably dead," he told the court.
"There had been no movement, no obvious signs of life that I had seen from my position for a number of minutes before that."
And he explained that the video clip showing him kicking the insurgent with his boot was in fact him "nudging" him to check for "signs of life".
In the course of two hours of questions from his barrister, Marine C said the tour to Afghanistan in 2011 was his first overseas deployment.
"It started off very quietly in terms of patrols," he told the board.
"We were patrolling every day but in terms of enemy activity there was very little."
Marine C said that for much of the tour he was the "point man" meaning he was at the front of the patrol using the valon metal detector.
He told the court that the first death of a British serviceman on that tour was a "massive blow to everybody's morale".
"It was the first incident that really brought home the consequences that being on ops in Afghanistan could lead to," he said.
And then 10 days later, his troop commander and another marine were killed by an IED.
"I think everybody was pretty devastated," he said "It was a serious loss to both our command post, the troop and the company - four people that we were all good friends with, absolutely devastating really.
"It was mixed emotions really. Obviously the gravity of the situation had further instilled the reality - things could very easily spiral out of control.
"But there was a definite feeling that we wanted to take the fight to the enemy and stop further incidents like this happening."
Marine C said the insurgent activity increased during the summer months - what he called the "fighting season" - following the end of the poppy growing season.
"Pretty much every patrol we went out on, we would find IEDs or come under small arms fire," he said.
Marine C said that by the September - after five months in Afghanistan - he was feeling "absolutely exhausted".
"I was drained, very stressed and constantly in fear really," he said.
He told the court martial he had been "keen for action" but that attitude changed as the tour progressed and he saw more and more of his friends killed or suffer catastrophic injuries.
"It changed as we began to take more and more casualties to the company and to the Commando as a whole, casualties and deaths," he said.
"It soon became apparent this was not a game.
"It soon became apparent this was not to be underestimated and the severity it had gravitated to.
"Towards the end of the tour I am sure that I and everybody else just wanted to get home without any more incident, just as quietly as possible."
Marine C said he coped with the stresses and strains of the tour by keeping his journal, which he said was therapeutic.
"I would use it as a vent - a way of outpouring emotions and thoughts and feelings," he said.
"Initially I thought it was a good way to keep a record of my first deployment overseas and would undoubtedly be a significant experience.
"We were advised in the pre-deployment briefs that a diary could be a good way of helping relieve stresses and strains during the tour."
Mr Tregilgas-Davey took Marine C through various extracts from the journal and asked him whether it was meant to be an "accurate chronicle of events".
Marine C said it was not.
He also said that he never had a conversation with Marine A about "ending up on a murder charge", which was written in his journal.
The serviceman said that any reference to "repeatedly asking" Marine A to shoot the insurgent was also not true.
Asked to describe the journal, Marine C said: "I would say they are the outpourings of someone who was in an increasingly challenging, stressful environment, who was also very angry and very frustrated."
Marine C told the board that he had lied during his interviews with the Royal Military Police last year when he said that no one had shot the insurgent.
Asked why, Marine C said: "Because I was protecting Marine A.
"Marine A was someone I had an immense amount of loyalty to and in my eyes he had taken me through my first operational tour and delivered me safely home at the end.
"He looked after us and I felt he had always done the best by us."