Niamh Ní Dhomhnaill had been with her partner for almost a year when she discovered that he’d been raping her while she slept. At the time, she was 25, and a language teacher in a Dublin secondary school. Her partner, Magnus Meyer Hustveit, was Norwegian. The couple had moved in together within a few months of meeting, but things were tense. It wasn’t a happy relationship.

On that particular night, Ní Dhomhnaill had been out with Hustveit and other friends, but left early, alone, because she felt unwell. “I’d only drunk water but I’d gone to bed and was out for the count,” she says. “I didn’t hear Magnus come back, which is unusual because I’d always been a light sleeper.”

When she did wake, she was no longer wearing her pyjama bottoms and had semen on her body. Magnus was sleeping beside her.

“I asked him: ‘Did you have sex with me while I was asleep?’ and he said, ‘Yes.’ I was so shocked and really confused. How could I not have known? I felt really ill, too, I was trying to figure it all out. I said: ‘I can’t give consent when I’m asleep. Don’t ever do that again.’”

But two weeks later, Ní Dhomhnaill awoke at 3am just knowing he had. “I said, ‘You’ve done it again – I felt it,’ and then I asked: ‘Have you been doing this regularly?’” “The whole time,” was Hustveit’s devastating reply. “He told me he’d been doing this on average three times a week ever since we’d been together.”

Her first response was to vomit. “I sat there heaving into a bucket,” says Ní Dhomhnaill. “I now know the physical reasons for that response, but at the time, I’d never experienced anything like that. It was a clear indication of the shock. It was 3am, I had nowhere to go, I didn’t know what to do.

“I left as soon as I knew there’d be a cafe open and my friend came to meet me. I told her that Magnus had been having sex with me in my sleep and she said: ‘That’s not ‘sex’. That’s rape.’ At that point, I couldn’t go there. I couldn’t use that word.”

It’s impossible to know how many women have been raped or sexually assaulted by their partners while they slept, although a recent piece of research has suggested the number might be far, far higher than we’d like to think.

In April, Dr Jessica Taylor, founder of VictimFocus, an independent consultancy and research firm working in forensic psychology, feminism and mental health, released a report on a study that had set out to gauge the extent of violence against women. Naming specific acts, rather than using broad – and loaded – terms such as “abuse” or “rape”, her survey asked more than 22,000 women if, for example, they had ever been spat at, or strangled, kicked or bitten. It also asked respondents if they had ever woken to their male partner having sex with them or performing sex acts on them while they slept. To this question, 51% answered yes.

This was not randomised sampling – the survey was widely shared online and participants were self-selected. For this reason, it’s hard to extrapolate from the findings. The results sparked a predictably polarised online response. “This was extremely validating for me after years of thinking, ‘Am I being raped?’ I’m not alone”, tweeted one woman. “It’s why I now jerk awake if someone even gently brushes against me while I’m sleeping, 13 years later,” wrote another. Other comments included, “Only chance I get!” and “the other half was OK with it!”

Katie Russell, spokesperson for Rape Crisis, says she was “not massively surprised” by the findings. “There isn’t a lot of research into the multiple ways women experience violence from known men, but we do know the numbers are so much higher than any official statistics,” she says.

“Rape myths are still incredibly pervasive. It’s commonly believed that if it’s your boyfriend or your spouse, if you’re sharing a bed, if you’re naked, if you consented earlier, then it can’t be rape. There is a really big difference between gently waking your partner and initiating sexual activity and actually doing something sexual or penetrating someone while they’re still asleep.

“The 2003 Sexual Offences Act is crystal clear,” she continues. “Consent can only be agreed when you have the capacity to make that choice – and if you’re asleep or unconscious, you don’t. We’re talking about rape – one hundred per cent.”

In Russell’s experience, rape while sleeping happens more commonly in abusive, coercively controlled relationships. In these cases, the psychology isn’t hard to understand. Martha*, 21, a student at the University of Oxford, who experienced such rape with her first boyfriend, believes it was all about power, his right to do whatever he wanted when he wanted.

“I was 16, I didn’t know what was normal in a relationship,” she says. “He was in the year above me and at the start it was really nice, but he became very abusive. He tried to control everything I did in all sorts of ways that I didn’t realise were wrong – where I went, what I could wear. I wasn’t allowed to smoke or chew gum. He’d log on to my social media to check on me.”

Twice, he slapped her and threw her against a wall, whacked the back of her head, and kicked her because he had seen her smoking on someone’s Instagram Story. (At the time, he was being unfaithful, but according to him, smoking was worse than cheating.)

“All of that, I’m over,” says Martha. “But to this day, probably the one thing that still affects me is the time he had sex with me when I slept.”

This happened in her single bed in her family home. They were spooning, with Martha sandwiched between him and the wall. “I woke up suddenly and realised what he was doing and just froze. It was towards summer and I fixated on a spot of morning light on the wall.

“I said nothing, never moved, never raised it with him, which is why I’m angry with myself to this day. I felt sick afterwards and in the morning, when he’d left, my 16-year-old self Googled it. I read that it was rape. Even now, if I’m sleeping with someone, I’ll never sleep against a wall where I can’t get out of bed easily and I always stay awake until I know they’re asleep – I haven’t had a proper relationship since.”

In Martha’s case, the rape happened once, but for some men, seeking sex with a sleeping woman is an active preference, a fetish known as somnophilia. Svein Overland, a Norwegian psychologist, is one of the few to have studied it – his interest sparked partly by his work in prisons, trying to understand the motivations of sex offenders, and also by his work with victims of what Norwegians call “after-party rapes” – attacks on vulnerable women who were either sleeping or drugged.

Overland believes somnophilia is part of the wider growth of what he calls “one-way sex”. His research into online porn showed a steep rise over the past decade in categories such as “sleeping sex”, as well as other forms of sex that are based on unresponsiveness, on only meeting your own needs. (“Flexi dolls” is another example – where women pretend to be sex dolls.)

These preferences overlap with porn itself, says Overland. “With one-way sex, with porn, with masturbation, there’s no dance, no seduction, no interaction and no pressure to perform,” he says. “The more I looked at this area, the more you see that a lot of men are afraid of having sex. Society is becoming more pornified but, at the same time, many studies show that people are becoming less sexually active. We have young men buying Viagra, unable to keep an erection.”

A sleeping woman is no threat – she’s absent, an object, a receptacle. When Overland asked sex workers in Oslo if somnophilia was something they encountered with clients, several had. “It wasn’t common, but it wasn’t uncommon, either,” he says. “One told me that she had customers that she really trusts so she has let them drug her so they can go ahead.”

As a kink between two consenting adults, somnophilia comes with rules and (problematic) terms such as “blanket consent” and “consensually non-consensual”. It requires deep trust and constant communication. However, it’s hard to believe that the 51% who responded to Dr Taylor’s survey come from this community, and for most women the impact can be devastating, says Russell.

“There seems to be a perception that something like this is a ‘lesser crime’ because it might not be at the hands of a stranger but your partner. But what would feel worse? Being pickpocketed by a stranger or robbed by someone you love and trust?” she asks. “The idea that you’re asleep so it didn’t require violence is also very dangerous. Penetrating someone’s body without their permission is an inherently violent act.

“Imagine being asleep and waking to find someone going through your personal things,” she continues. “Now imagine it’s your actual body that has been intruded into.”

For Ní Dhomhnaill, the fact that she’d been sleeping, and for some inexplicable reason hadn’t woken, was terrifying. (She asked Hustveit if he had drugged her, especially since by the end of the relationship, she felt ill and permanently exhausted, but he has denied this.) “Because the memories I have are so vague, it leaves you with this sense of uncertainty and guilt and shame,” she says. “When we only have bits of information, our brains tend to fill in the gaps.

“When I first left him, I wouldn’t sleep. I’d lie awake all night and have hallucinations – him raping me. Those flashbacks, that trauma response, was the mind and body trying to piece things together. Even now, nine years on, I still wake at two every morning. I don’t even need to check the clock. We know that the body stores memories of trauma – and I think 2am is when it used to happen.”

How hard is it to successfully prosecute these cases? Given that recent Home Office figures showed that, in England and Wales, fewer than one in 60 recorded rapes resulted in a charge, the answer, says Russell, is very hard. “I don’t want to discourage people from reporting,” she says. “If it happens, it’s a crime and cases have been prosecuted. But when there’s no physical evidence, no witnesses, sometimes no recollection … there are added challenges.”

Lisa*, 40, did report her former partner for raping her while she was asleep. It had happened at the start of 2019 after they had separated and Lisa was treading a difficult line, trying to remain amicable, to avoid what she knew could be a bitter custody battle over the couple’s daughter. “He’d always been extremely domineering, whether it was over what I wore, what I bought, where I put things in a room, where we went,” says Lisa, “and he never respected boundaries. He’d choked me during sex before, he always did what he wanted.

“On that night, I’d made dinner. He’d drunk too much so I let him stay in the spare room – but I woke up to find him in with me, having sex.”

The next morning, she went to her local police station. “I wasn’t sure if I was overreacting,” she says. “Two officers asked if he had forced himself on me? No, I’d been asleep. He didn’t pin me down, there was no struggle. They said they weren’t sure there’d been any crime here.”

The next day, a sergeant rang Lisa to say he’d read the officers’ report and was concerned that this hadn’t been recognised as rape. “He actually rang a few times but I didn’t want to talk about it,” says Lisa. “They’d lost my trust.”

Ní Dhomhnaill never doubted that she wanted to prosecute Hustveit. “It was really clear to me that his behaviour was dangerous, it was a pattern,” she says, “but I had no evidence. The only action available was to get him to admit it.”

She sent him an email asking exactly what he had done and why – and, to her shock, he responded almost immediately with a great deal of detail. “It was clinical, procedural, there was no sense of atoning. He seemed completely detached from his words. The reason he gave was just his own gratification. At the end, he said: ‘You could have me prosecuted and I really hope you don’t.’”

She did. In July 2015, Hustveit pleaded guilty in Ireland’s central criminal court to one charge of rape and one charge of sexual assault. He received a seven-year wholly suspended sentence but the next year the court of appeal in Dublin found this “unduly lenient” and Hustveit was jailed for 15 months. Ní Dhomhnaill also launched high court civil proceedings seeking damages for multiple acts of rape and sexual assault while she slept.

In February 2020, she told the jury: “There has never been a part of me that has not been profoundly impacted,” and that in the immediate aftermath, she suffered PTSD and had tried to take her own life. She said she had felt “unsafe everywhere”, frightened to trust anyone, even her parents. Hustveit offered no defence and the jury awarded damages of €1m (£863,000).

The last nine years have been a slow but solid process of recovery. Ní Dhomhnaill, now 34, retrained as a psychologist, and is currently in clinical training. She believes her past makes her better at her job. “I think the beautiful and important thing I can bring when I’m in the room with someone who is hurting, who is suicidal, is that sense of hope,” she says. “Even if they don’t believe it, I know myself that something can change, something can shift, and so I can hold that hope for them.”

Yet, despite everything, she still catches herself doubting everything that happened to her and her own response. “At times, I still have thoughts that maybe I just made a big deal out of nothing – I still think that to this day,” she admits. “I think that’s an indictment of the world we live in.”