The man, 42, who has name suppression, was convicted earlier this year

A man who claimed he had a sleep disorder that made him engage in sexual behaviour while asleep has been sentenced to five years jail for rape.

The man, 42, who has name suppression, was convicted in August of raping and indecently assaulting his wife over a five-year period.

He was sentenced in the Auckland District Court on Friday morning supported by a large contingent of friends and family.

Part of his defence had involved claims of suffering from a rare disorder called sexsomnia, where a person engages in sexual behaviour while asleep.

His 44-year-old former wife, who also cannot be named, says at first she chose to believe her husband, rather than accept she was married to a "monster".

The woman said they were married in 2007, after a traditional Christian courtship where there was no sexual contact.

But soon after the wedding, her husband became extremely sexually active.

Five months into their marriage the woman awoke to find her husband pinning her down and engaging in aggressive sex.

"He was a thief in the night," she said.

GOOD PARENT

The man's defence lawyer Paul Dacre said his client was an active and positive member of the community and a good parent. His mother and brother and others who had written references in support of the man were in court during sentencing.

Dacre acknowledged a breach of trust and said there was some vulnerability, though that was present in any relationship, but he called the case a strange one with no previous precedents.

In sentencing the man, Justice Gibson said this was the man's first appearance in court on serious criminal charges.

He spoke about the man's exemplary behaviour to his wife's children and another foster child. "Nevertheless for part of the marriage there appeared to have been difficulties between you over sexual activity. It goes without saying that marriage is not a licence to indulge in non-consensual sexual activity."

He said there had been no cruelty or brutality in this case and gave discounts to the man's sentence for his clear criminal record leading up to this case and a previously exemplary life as set out by a number of references from people with significant standing in the community.

The man was sentenced to five years in prison.

WHAT IS SEXSOMNIA:

It is a rare condition in which the sufferer initiates or engages in sexual activity while sleeping.

Mary Hudson, a therapist from Sex Therapy New Zealand, said she had dealt with a number of people who suffered from the condition in varying degrees.

"Some people are just talking about waking in the night in the middle of some kind of sexual activity, others are talking about being told the next morning of full-on sexual intercourse which they haven't been aware of."

Although quite frequently there were couples who engaged in sexual activity while half-asleep, sexsomnia was relatively uncommon, she said.

Sleep specialist Andrew Veale said he had dealt with only a small number of sexsomnia cases.

It was related to sleep-talking or sleep-walking. "It's uncommon but probably grossly under-reported."

It was always a contentious issue as there were generally no witnesses.

"There is no question that it is a legitimate condition. The problem with all of these cases is whether it was legitimate on the night in question."