A psychiatrist called by the prosecution told a jury today even she did not believe a man who killed his wife during a nightmare should be locked up in a mental hospital.

Dr Caroline Jacob said Brian Thomas, aged 59, did not require treatment and the chances of him killing someone else in similar circumstances were "incredibly low."

Thomas, from Neath, strangled his wife Christine while the couple slept in a camper van during a short holiday near Aberporth.

Thomas had been accused of murder, which he denied. By the time his trial opened at Swansea crown court both the prosecution and the defence had accepted expert opinion by psychiatrists that he had been suffering from a sleep disorder that amounted to automatism.

In that state, said Paul Thomas QC, prosecuting, it was now accepted he had not been in control of his actions.

He said that, in an extremely rare case, the jury would now have to decide only if the degree of automatism amounted to a form of insanity. The only verdicts available to the jury are not guilty of murder due to insanity or simply not guilty.

During cross examination today, Elwen Evans QC, the barrister representing Thomas, told Dr Jacob that, under the law, should Thomas be found to have been insane then the judge would have to make a hospital order under which Thomas would be forcibly detained in a mental hospital.

Dr Jacob said in her opinion Thomas was indeed insane at the time of the killing. But she did not believe he should be detained, or that any psychiatric treatment was necessary or would have any effect.

Dr Jacob said she worked at Broadmoor, which held some of Britain's most dangerous and mentally ill criminals, and "he does not belong there."

She said she favoured an absolute discharge, under which Thomas would walk free from court.

She also agreed that it would be "reasonable" for another psychiatrist to conclude that Thomas had not been insane at the time of his wife's death.

The jury has been told that the issue in the case would be whether they believed Thomas' automatism had been caused by internal or external factors. Internal, said Dr Jacob, which she favoured, would equate to insanity whereas external would not.

Thomas, it has been said, regularly suffered from sleepwalking, during which he would sometimes act strangely.

He and his wife of 40 years slept in separate bedrooms at home but in the same room while enjoying holidays in their camper van.

In July, 2008, they drove to Aberporth and stayed in a vehicle park for the night.

During the night the couple could hear a group of "boy racers" screeching outside and became so concerned Mr Thomas moved the van to another area of the park.

Shortly before 4am the following morning he made a 999 call in which he said he had killed his childhood sweetheart during a dream in which he thought he was being attacked inside the van by one of the boy racers.

A tape of the call was played in court and Thomas wept as he heard himself saying, "I woke up fighting one of those boys but it wasn't a boy, it was Christine.

"I think I killed my wife. I killed her. Oh my God.

"There was no boys, it was me. I must have been dreaming or something.

"I love her. What have I done? She's my world."

Mr Thomas later told police he had dreamt of a man crawling across the bed, putting him in a headlock, then waking to find his wife dead.

Thomas was arrested and for a while detained in a secure mental unit before being released into the care of the couple's two daughters.

Later, he was charged with murder and detained in custody once more.

Mr Paul Thomas QC said the Crown Prosecution Service has been "highly sceptical" of his explanation. But tests had been carried out and experts now agreed he had suffered from a serious sleep disorder and that the killing had been involuntary.

The prosecution was so concerned about other people carrying out "copycat killings" that when the experts gave evidence they would not go into too much detail.