A former soldier who stabbed his two neighbours to death had depression but was not otherwise mentally ill, two forensic psychiatrists agreed.

Collin Reeves admitted stabbing Steven and Jennifer Chapple in their home in Norton Fitzwarren outside Taunton in Somerset, on November 21 last year, but denied murder.

The Afghanistan veteran instead admitted manslaughter on the grounds of diminished responsibility.

Jurors were asked to decide whether Reeves’ depression – which was diagnosed as “moderate” by one psychiatrist and “mild” by another – amounted to an “abnormality of mental functioning” in law.

On Friday, Reeves was convicted of murder.

During the trial at Bristol Crown Court, the jury heard Reeves and his wife Kayley had been involved in a dispute with the Chapples about parking since the previous May.

The Reeves also had problems in their marriage, and around 40 minutes before the killings Mrs Reeves had asked her husband for a trial separation.

The defendant later said he had almost no memory of the incident, and that he did not have the “depth of feeling” about the Chapples that would explain why he killed them.

Forensic psychiatrist Dr Lucy Bacon, who assessed Reeves on behalf of the defence team, concluded that he had been suffering from moderate depression at the time of the attacks.

Dr Bacon said she had explored the possibility that he had been suffering from post-traumatic stress disorder as a result of his tour in Afghanistan, and concluded that he was not.

The defendant reported being anxious in crowds but was not “hyper vigilant” – a symptom of PTSD often seen in soldiers where they feel a constant sense of threat.

He was also not suffering from nightmares or flashbacks.

Instead, Reeves told her that since leaving the Army in December 2017 he had been suffering from low mood and tiredness and wanted to avoid people.

Reeves said he had been considering suicide, and also about packing his bag and going missing to get away from his life.

While at the police station, Reeves gave his name as “Lance Corporal Collin Reeves” and gave his service number, and seemed confused as to why he was there.

Dr Bacon said it appeared that the defendant had “regressed” to his training.

“He’s spent many years as a soldier and he’s gone back into that mode of answering questions with his service number, that sort of thing,” she said.

“I think that was caused by the shock of having killed the Chapples.”

Both Reeves’ wife and his mother Lynn Reeves described Reeves looking very different on the night of the attack, something Dr Bacon attributed to extreme shock.

Reeves told Dr Bacon that life before the stabbings “felt dark all the time”.

He told her he had felt scared a lot of the time growing up due to episodes of domestic violence against himself and his mother by his father, but had never sought help for his mental health.

Reeves said “I’m a soldier and I need to toughen up, so I don’t discuss it,” Dr Bacon said.

She diagnosed his depression as moderate, because he was still able to function in some aspects of his life, such as going to work or going for a run, and worried about providing for his family.

Dr Bacon said depression was an abnormality of mental function because it affects how someone sees the world and their own behaviour.

But she said in her opinion it did not meet the criteria of diminished responsibility in law.

Dr John Sandford, for the prosecution, said Reeves’ loss of memory of the killings was consistent with “dissociative amnesia” – where an incident is so traumatic the brain erases it.

“This is nothing to do with depression – it’s a reaction to a traumatic act, something that is usually a reaction to something you’ve done rather than something done to you,” Dr Sandford said.

The witness diagnosed Reeves with mild depression, adding that it was a normal response for someone who was unhappy in his job and unhappy in his marriage.

Dr Sandford said Reeves’ demeanour of shock, confusion and memory loss when he was arrested were a consequence of the killings, not pre-existing mental conditions that drove his actions.