London: A sex attack victim said yesterday that she has been betrayed by British justice after her attacker walked free from court citing his “sexsomnia”.

The woman, a married teacher, said she was subjected to a violent assault by Paul Fallon, 41, as she slept next to her husband at a friend’s house.

But the court accepted Mr Fallon’s explanation that he was asleep at the time of the alleged assault, which happened after a birthday party.

His wife also gave evidence in his defence, saying he would sometimes have sex with her while asleep. The victim has written to Director of Public Prosecutions Keir Starmer to request a review of her case and other “sexsomnia” cases.

She claimed in court that Mr Fallon was awake during the assault and said later that the Crown Prosecution Service failed to question his sleepwalking account properly. The CPS appeared to have breached its own guidelines that sleepwalking defences should be “robustly challenged”, she added.

A jury found Mr Fallon not guilty “by reason of insanity” because he could not control his actions while asleep.

He was allowed to walk free from court yesterday despite the judge admitting that he posed a “serious risk” to others.

The woman, a 42-year-old mother-of-two, has branded the treatment of her case “shambolic, disgraceful and inept”.

She said: “I was assaulted where I should have felt safest, in the arms of my husband. I called the police and went through the ordeal of giving evidence because this man violated the sanctity of my marriage. During the trial I suffered an extremely unpleasant and traumatic cross-examination, only to then find out that the CPS weren’t even challenging his sleepwalking defence.

“I was violated by this man and then I was betrayed by the CPS. I am now having to have counselling as I became continually tearful and anxious after the assault and I suffer horrific nightmares.”

The case is the latest in a series of controversial trials in which men have claimed they cannot be held accountable for rapes or sexual assaults because they suffer from the rare sleep condition known as parasomnia, nicknamed “sexsomnia” because of its use as a defence in sex crime trials.

Following the attack, Mr Fallon was assessed for three nights at the private Edinburgh Sleep Centre and diagnosed with a sleep disorder after a doctor hired by the defence saw his arms and legs move while he was asleep.

But the prosecution’s medical expert did not assess Mr Fallon independently and both of these doctors worked for the same chain of private clinics.

Neither expert was called to give evidence or face cross-examination at the trial and the jury was simply presented with their reports that Mr Fallon suffered from a sleep disorder.

The woman, who cannot be named for legal reasons, said: “It is a farce that the CPS didn’t challenge his defence properly. The law needs to change to stop other victims being let down by justice.”

The attack happened in February 2012 after the woman and her husband celebrated a friend’s birthday at a Northamptonshire restaurant.

Mr Fallon, a self-employed marketing consultant, and his wife Magz, 40, were also there and several couples returned to a friend’s house after the meal.

He had been drinking heavily and was left to sleep on a sofa while his wife went alone to a hotel. The victim and her husband slept on a bed in the same room as Mr Fallon. She said she was still wearing her tights and underwear when she woke to find Mr Fallon attacking her.

“I was lying on my side, curled up, and he grabbed my shoulder and flipped me onto my back,” she said.

“I stopped him and he got up and tried to run away. I was screaming and hysterical and I called the police immediately.”

The attack lasted seconds and her husband only woke when she started screaming.

Mr Fallon was charged with sexual assault and stood trial at Northampton Crown Court in August.

The jury was told he suffered from insane automatism, a defence which means a defendant had no conscious knowledge of his actions and cannot be held responsible for them. The jury found Mr Fallon was not guilty “by reason of insanity”, a rare verdict which meant he was still put on the Sex Offenders Register for five years and was told to undergo medical treatment.

Mr Fallon, who shares a £1.5 million home in affluent Farnham Royal, Buckinghamshire, with his wife, has agreed to pay the £3,900 bill for a year of private treatment for his sleep disorder. The judge also imposed a Sexual Offences Prevention Order banning from him from sleeping at friends’ homes or any private home unless he has previously told householders he suffers from a sleep disorder and given details of his conviction.

Judge Lynn Tayton QC said he had been assessed as posing a “medium risk of serious harm” to others, and said the risk would rise if he slept near women.

She said: “Steps must be taken to reduce the risk which, in my view, you still pose... It seems to me that I have to have an eye to the protection of the public.”

The victim says in her letter to Mr Starmer: “Having experienced the trauma of my case being handled in such a shambolic manner, it is not surprising women are unwilling to report sexual crimes to the police.” The CPS said it did seek to challenge the defence’s medical evidence. Its website sets out its policy on sleepwalking defences, saying: “It is essential that this defence is robustly challenged.”

Micheal Neofytou, defending Mr Fallon, said: “He was effectively not culpable for those actions.”

Mr Fallon’s solicitor, Phil Smith, said: “My client is content that the jury accepted the account he provided from the start was the truth.

“Three experts were instructed and examined him - one by the defence and a second by the prosecution. The third - jointly appointed by the prosecution and defence - then endorsed the findings of the first two. All three experts agreed his actions occurred while in a sleep-induced state.”