A LEADING doctor has told a jury that a rape accused may have been unaware he was having sex because of a condition called ‘sexsomnia’.

Dr Ian Morrison, a consultant neurologist with NHS Tayside and a specialist in sleep medicine, said it was “entirely possible” that Darrell Swanson’s defence that he was asleep when he carried the alleged sexual assaults on a woman and her sister was true.

He told the High Court at Livingston: “It’s almost exclusively the case that there’s a lack of recall. Generally speaking patients do not recall.

“Some see it as a bit of a joke and laugh it off. Some find it very embarrassing and some are sympathetic to the position.”

Asked about Swanson’s admitted episodes of “nocturnal groping behaviour” – grabbing the breasts and thighs of women he slept with – the doctor said that could be another symptom of the condition.

He added: “Sexual behaviour in sleep isn’t exclusively sexual intercourse. It can include dirty talking, masturbating behaviour and touching inappropriate parts of the body during sleep.

“He has a history of sleep walking, also jumping out of his bed because he thinks things like spiders are in his bed. We know from his current wife that he talks in his sleep as well.

“In a forensic setting such as this it’s very important to look at the whole presentation. The fact he’s got a history of other forms of sexual behaviour in sleep is relevant.

“He's by definition asleep when it’s happening. It’s extremely unusual for a patient to have any recollection of these behaviours. It’s almost unknown.”

He said factors such as sleep deprivation, stress, anxiety or drinking alcohol could trigger a sexsomnia episode, but admitted there was no diagnostic test for a sleep disorder.

Advocate depute Mark Mohammed asked Dr Morrison if the accused saying something like “let me finish” to the older woman when she wakened was compatible with him being asleep.

The consultant replied: “That would imply he had awareness of the situation and wouldn’t be compatible with sexual behaviour in sleep.

“It would imply he was awake and having sex through intent.”

Swanson, 39, who lives in Dunfermline, Fife, denies repeatedly raping a 36 year old woman while she was asleep and incapable of consenting at an address in Lochgelly on various occasions between January 2006 and December 2009 and on a single occasion between June and July 2013.

He also denies raping the woman’s younger sister at the same address in April 2006 when she was 15 or 16 years-old, asleep and unable to consent.

Swanson admitted in evidence that he had sought medical help for an addiction to porn and masturbation but refuted suggestions that he had taken sexual advantage of both women while they slept.

Neither of the women involved can be identified for legal reasons.

The trial, before Lady Poole, continues.