An off-duty Brighton soldier facing jail for stealing a rifle and ammunition from his barracks has denied lying about seeing horrors in Afghanistan and suffering war-zone trauma.

Corporal Harry Killick, 36, has pleaded guilty to possessing a prohibited weapon and stealing a firearm and ammunition from a Territorial Army barracks in Brighton, East Sussex.

Killick claimed he had post-traumatic stress disorder (PTSD) after witnessing people being killed and injured during a tour of duty in Afghanistan lasting just under six months.

In interviews with police, the probation service and psychiatrists, Killick said he witnessed comrades being killed during his tour with the Princess of Wales' Royal Regiment, Lewes Crown Court heard.

Killick, from Brighton, also said he had to take part in the grisly task of retrieving DNA from the body parts of an insurgent killed during a battle.

But some of Killick's comrades have called into question his account, and a Newton hearing is being held to determine the facts of the case.

In the witness box, Killick categorically denied that he had made up his experiences at war, or that he had exaggerated his symptoms for PTSD.

Defence counsel Stephen Wedd asked him: "It's suggested, at best, that you have exaggerated your experience in Afghanistan. Do you think you have?"

Killick replied: "No, not at all."

Mr Wedd added: "It's being suggested, at worse, that you plain lied. Are you lying to Your Honour, the judge?" Killick responded: "No, I'm not."

Mr Wedd went on: "It's suggested that if you didn't exaggerate or lie, that you are lying about your symptoms. Are you exaggerating those?"

Killick replied: "No."

Under cross-examination from prosecutor Oliver Dunkin, Killick was told that the theft from the barracks came seven months after his demobilisation from Afghanistan.

Mr Dunkin said that the trigger for the theft from the barracks came on October 19 2012 after Killick was told that he would not be joining comrades on a shooting practice weekend amid fears for his mental state.

"What I'm going to suggest is that your breakdown, culminating in that night with the gun, has more to do with your personal circumstances than anything to do with your experiences in Afghanistan," Mr Dunkin said.

Killick said: "I disagree, totally."

Mr Dunkin went on: "That it's to do with the breakdown of your relationship, your debts, the way your ex-girlfriend treated you, and not to do with your job in Afghanistan."

Killick responded: "I totally disagree." Mr Dunkin said Army colleagues offered him help securing a job after the tour ended in March last year.

And Mr Dunkin questioned Killick's account that he had seen people killed and injured in conflict. Mr Dunkin told him: "Cutting to the chase, you didn't see anyone injured or killed, did you?"

Killick said: "I did. I saw people killed and I saw some of my own patrols, not majorly, but injured in a way."

Earlier, the court heard statements from medical experts who reached conflicting conclusions on whether Killick was suffering from PTSD.

Killick told psychiatrist Dr Roderick Ley that he experienced problems with his mental state after he was sent on tour.

On his return, he said he should have been given a period of leave but instead was asked by Army officials to go to Cyprus in spring 2012.

In his report, Dr Ley said Killick described becoming withdrawn, suffering sleep problems, flash-backs to his time in Afghanistan, and nightmares.

Two incidents stood out, Killick told him, including coming under fire from insurgents while he had no air support after being asked to go to a village.

The second incident Killick said played on his mind related to a man standing on a pressure plate which failed to detonate properly.

Months after his return to Britain from action, Killick told Dr Ley that his health worsened, resulting in him travelling to Beachy Head after saying he could no longer cope.

Dr Ley said Killick's symptoms were consistent with PTSD but he felt it was "highly concerning" that his account of events in Afghanistan did not match the Army's.

There were three possibilities - that Killick was being untruthful, that he believed the experiences occurred when they did not, or that the Army was being untruthful, he added.

"In my opinion, Mr Killick has falsified his symptoms of PTSD," said Dr Ley. "The most likely explanation is that he suffered from adjustment disorder."

However, his conclusion was at odds with that of another psychiatrist, Dr Derek Tracy, who said there was nothing in Killick's demeanour to doubt his account.

He said: "I have considered whether Mr Killick is malingering in relation to his symptoms and I do not believe that he is.

"He was quite reluctant to recount his experiences and found them emotionally taxing." He added that Killick's symptoms have become worse since being held in prison.

Major Ross Noot, who earlier this year was second in command of the PWRR, said Killick seemed fine when he was interviewed upon demobilisation.

He said: "I would describe him as upbeat. He said he was disappointed at leaving early, in common with TA colleagues. He said he enjoyed his time and the company of 5 Platoon.

"He said it had been a roundly positive experience. The sense I had as he left was that he would volunteer to do it again in the future."

The case was adjourned to 10.30am tomorrow.