The Sexsomnia Defense: Law, Medicine, and Strategy

By Joshua Saunders and David Marshall

“I woke up and found my hand on my daughter, rubbing her genitals.” Our client, an educated professional, sat in the office explaining how he came to be charged with child molestation. We glanced at each other dubiously. Could a jury possibly believe such a story? 

It did. After hearing testimony from our client and a leading sleep medicine physician, a jury acquitted him.

Our client didn’t know it the night he agreed to sleep on the floor next to his daughter after a family movie night, but he suffers from sexsomnia. The term “sexsomnia” sounds like the invention of a defense attorney desperate to excuse potentially criminal actions. But the condition is recognized in the two most authoritative manuals for sleep disorders: The Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5), the most widely respected reference manual for mental disorders generally, and the International Classification of Sleep Disorders, 3rd Edition. Sexsomnia was first recognized in 2003 but reports of apparent cases appear in medical literature published as long ago as 1985. 

Our client is not alone. A 2010 cross-sectional study in Norway found that 7.4 percent of the people surveyed had experienced a sexual act while asleep.11 B. Bjorvatn, et al., “Prevalence of different parasomnias in the general population,” Sleep Med. (2010): 1031-4. A study from a Canadian sleep clinic that same year showed that 7.6 percent of 832 patients had experienced an episode of sexsomnia; 11 percent of males were affected, and 4 percent of females.22 S. A. Chung, et al., “Frequency of sexsomnia in sleep clinic patients,” Sleep, no. 33 (2010): A226.

In this article, we describe the medical science behind the condition, identifying for attorneys indications that a work-up for sexsomnia is needed. Then we turn to the scant case law relevant to defenses based on sexsomnia and other parasomnias. Finally, we offer some practical tips for using sleep experts and a parasomnia diagnosis in court—things we learned recently while building and presenting our client’s defense. 

Sexsomnia, also called “sleep sex,” is defined as “abnormal sexual behavior during sleep.”33 M. Anderson, et al., “Sexsomnia: Abnormal sexual behavior during sleep,” Elsevier Brain Research Reviews 56 (2007). It’s a type of parasomnia, a category of sleep disorder of which the most common type is sleepwalking. Parasomnias are simply an undesirable physical event that occurs while asleep, while falling asleep, or while awakening. 

Parasomnias can be divided into two categories—those that occur during rapid eye movement (REM) sleep and those that occur in non-rapid eye movement (NREM) sleep. REM sleep is the stage of sleep when most dreams happen. It makes up about a quarter of our total sleep time, and brain activity during REM sleep looks much like brain activity while awake. Parasomnias that occur during REM sleep are not relevant to sexsomnia. They mostly involve acting out dreams; they can be an early sign of Parkinson’s disease. 

The majority of parasomnic activity occurs during NREM sleep. NREM sleep is divided into three stages and consumes 75 or 80 percent of our total sleep time. NREM parasomnias are known as “disorders of arousal” because they occur when micro-disturbances rupture the otherwise deep NREM sleep. These disturbances don’t bring a sleeper to full consciousness; rather, they rouse the sleeper enough that—if they have a predisposition toward parasomnia—they are vulnerable to experiencing an episode. 

Three NREM parasomnias are identified in the scientific literature: sleepwalking, sleep or night terrors, and confusional arousals. In each of them, a sleeper partially awakens from deep sleep. The sleeper’s eyes open, but they are often glassy and seem to stare without comprehension. An episode can last as long as 40 minutes and can be accompanied by semi-coherent “sleep talking.” A sleeper who is brought from an episode to full consciousness—often with difficulty—typically does not remember much; they have partial or complete amnesia for the experience. 

Night terrors are not nightmares—nightmares occur during REM sleep, not NREM sleep. In a night terror, a person (often a child) sits upright in bed, screaming in fear. Much like a sleepwalker, they cannot be easily awakened and do not acknowledge people around them. 

“Confusional arousals” is the category that embraces most parasomnias other than sleepwalking and night terrors. The sleeper partially awakens from deep sleep and appears confused or acts strangely. Confusional arousals are sometimes called “sleep drunkenness” because the sleeper can appear sluggish and confused, as if intoxicated. 

But behavior during a confusional arousal can also be quite sophisticated. Dr. Clete A. Kushida, the Stanford sleep medicine specialist who testified in our case, once had a patient sit up in bed during a sleep study and throw toiletries at him and a technician; the patient’s eyes were open as he tracked his two human targets around the room. According to Kushida, people can “do practically everything they normally would do during the daytime when they are asleep.”

Sexsomnia is a confusional arousal, distinguished from the others by sexual behavior during sleep. The sexual behavior can take many forms. Kushida says that “while the majority of sexsomnia cases involve masturbation or fondling, [many] involve actual intercourse. Patients are often told by their partners that they have engaged in sexual intercourse with them, but the patients have no memory of doing so.” There are also many examples of apparent sexual assaults in medical literature. One study found that partners report that persons experiencing sexsomnia can be more aggressive, less inhibited, and less focused on their partner than they usually are—and sometimes they display sexual behavior that is unusual for them. Kushida, too, notes that “the behavior does not appear to have a correlation to an individual’s awake sexual preference or interests.”

According to Kushida, “Sexsomnic behavior appears to be fairly random, in the sense that individuals who are predisposed to have this behavior will have it with whoever is in the bedroom at the time.” 

The causes of sexsomnia are not clear, but it is clear that most sufferers have a family history of parasomnias. Many walked in their sleep as children. Our client is like many in that his intimate partners had told him in the morning that he had made amorous advances during the night—advances he did not recollect at all. 

While the causes of sexsomnia are unclear, the precursors of an episode have been identified. If a person is genetically predisposed to sexsomnia, a variety of stimuli can trigger the micro-disturbances (the “fragmentations” of NREM sleep, as sleep scientists put it) that can lead to an episode. 

Some of those are internal stimuli, such as sleep apnea. A person with sleep apnea suffers momentary breathing interruptions during sleep. The resulting oxygen deprivation can trigger fragmentation (and snoring like a freight train, as bedpartners of those with apnea know). The movements that go with restless legs syndrome can trigger sleep fragmentation, too. Each tiny disturbance in sleep increases the chance of an episode. Stress, sleep deprivation, and diverging from one’s normal sleep routines also increase the chance. 

Alcohol and recreational drugs increase the chance of an episode, particularly for a person with sleep apnea. Alcohol is a central nervous system depressant and so can worsen apneas. There are also prescription drugs that can make an episode of parasomnia more likely—most antidepressants, for example. Lexapro has been shown to double the chance of a sleepwalking episode.44 M. Ohayon, “Prevalence and comorbidity of nocturnal wandering in the U.S. adult general population,” Neurology 78 (2012): 1583-9. Lipitor, the statin for high cholesterol, has also been associated with sleep disturbance.55 Marco Tuccori, et al., “Neuropsychiatric adverse events associated with statins: epidemiology, pathophysiology, prevention and management,” CNS Drugs 28 (March 2014): 249-72.

External stimuli can also create a micro-disturbance in sleep. A sexsomnia episode can result from an unfamiliar event or situation during sleep—such as sleeping in an unfamiliar place or with an unfamiliar bedmate. A loud noise—a barking dog, a siren—can lead to a partial arousal. Sleep medicine physicians often advise their patients to eliminate as many sensory stimuli at night as they can to minimize the chance of an episode. 

A sexsomnia diagnosis is rare.66 Sleep medicine physician Clete Kushida sees one or two sexsomnia cases a month. About 10 percent of them come to him in connection with criminal prosecutions. Some health care providers are hesitant to diagnose it. James Olsen, a mental health counselor and certified sex therapist in Bellevue, believes the hesitation stems at least partly from “a lack of comprehensive education concerning sleep disorders.”

A parasomnia defense to a criminal charge negates mens rea. Throughout the history of American criminal law, culpability has generally required both a wrongful act and a wrongful state of mind. There are volumes devoted to the nuances of the mens rea requirement, but the basic idea has always been that a person cannot be responsible for a crime they did not know they were committing. 

Washington law recognizes that an actor who is asleep is not criminally responsible for their actions. Sexsomnia is not discussed much as a disorder or as a defense in many cases, but case law does deal generally with parasomnias and their consequences. 

In recent years, Washington appellate courts have grappled with sexsomnia defenses in two child sex abuse prosecutions. In State v. Pratt, 11 Wn. App. 2d 450 (2019), the defendant was accused of child molestation and sought to have an expert testify about sexsomnia. The trial court excluded the evidence, finding it a disguised attempt at a diminished capacity defense. 

The Court of Appeals affirmed the conviction but rejected the trial court’s analysis. It said that sexsomnia is different from diminished capacity. Rather, it said, a sexsomnia defense is a defense of involuntary action, also known as automatism. “The defense of involuntary action as a result of being asleep, therefore, should not be treated as one of diminished capacity. Instead, involuntariness due to sleep is an affirmative defense that must be proved by the defendant by a preponderance of the evidence.” State v. Pratt, 11 Wn. App. 2d at 463, following the Washington Supreme Court’s analysis in Washington v. Deer, 175 Wn.2d 725 (2012). In Pratt, the court found, the defendant had not met the evidentiary burden for the defense because his expert was unable to testify that he suffered from sexsomnia on the night in question or any other time. 

In Deer, a woman in her 50s maintained that she was asleep during sex acts with a 15-year-old boy. The court rejected her argument that the state should have to prove that she was awake as an element of child rape. Instead, it held—for public policy and other reasons—that sexsomnia is an affirmative defense. The court noted that the defendant is the party more likely to have access to the relevant evidence. 

This question arose again in Washington v. Blake, 197 Wn.2d 170, 214-15 (2021), the decision finding Washington’s felony drug possession law unconstitutional. The court in Blake ruled that the drug possession statutes punished innocent and passive conduct and so violated due process. It distinguished Deer on the basis that rape is a strict liability crime and so requires no mens rea. But Justice Debra Stephens’ opinion, concurring in part, argued that the majority’s reasoning implied that criminalizing child rape without a mens rea element also unconstitutionally punished innocent and passive behavior. 

In civil law, there is little case law mentioning parasomnias. In Carr v. Michelson, No. 47668-8-I, 2002 Wash. App. LEXIS 1715 (Wash. Ct. App. July 22, 2002)(unpublished), Carr sued a cruise ship for firing him after he was accused of sexual harassment. He asserted he had been sleepwalking when he got into bed with another employee. Neither the trial court nor the Court of Appeals seemed to believe this, but both held that it didn’t matter, as the employer was entitled to fire Carr simply because the complainant perceived his appearance in her bed as sexual harassment. (That Carr was among a group of pranksters who had placed a large ice sculpture of a penis in the complainant’s cabin probably did not help him.)

If you suspect a parasomnia affected your client’s behavior, have the client undergo a polysomnography as soon as possible. A polysomnography is a sleep study, done in a lab, in which a patient is monitored during a night of sleep. Sensors monitor eye movement, brain activity, air flow in the nose, oxygen in the blood, and involuntary movement of the legs and arms. You may have to schedule polysomnography months in advance. 

The results can provide powerful evidence. Polysomnographies produce graphs of sleep fragmentation and respiratory disturbances that make strong trial exhibits. In our case, our client’s respiratory index, which measures apneas and other moments when the airway is blocked, was nearly 20—and anything above 5 is considered abnormal. And his index of periodic limb movements was three times the normal value. 

Since the client is asleep when polysomnography data is being collected, an argument that they were malingering won’t go far.

You also need to interview your client’s blood relatives. Susceptibility to parasomnias often runs in families. You want to learn of parasomnias experienced by the relatives as well as hear their memories of parasomnic behavior by the client. Our client’s mother remembered his sleepwalking as a small child (and urinating once in a pantry and another time in a backyard swimming pool). Relatives also testified at trial to episodes of sleepwalking and sleep conversations by other members of our client’s extended family. Family members are usually biased witnesses, of course, but their accounts can still be key factors in an expert’s diagnosis. 

When the case is tried, make sure you speak to the nuances of intent. Ideally, your expert witness will explain that actions taken while asleep are not the product of intent. Although the word “intent” does not appear in the jury instructions in a Washington child molestation prosecution, its synonym “purpose” does. One element of the crime is “sexual contact,” which is contact with sexual or other intimate body parts “done for the purpose of gratifying sexual desire.” Our jury told us after the acquittal that they had wrestled with this question: Even if asleep, did our client still touch his daughter’s genitals “for the purpose of gratifying sexual desire”? Your expert should discuss the involuntary, unconscious nature of actions taken during an episode of sexsomnia.

A client who suffers from a parasomnia may need more than legal help. They may need practical advice on protecting themselves and others. Dr. Kushida had a patient who learned he had to lock his car keys in a safe at night to stop his practice of driving his car a few blocks in his sleep and then walking home. (In the morning he would have no idea where his car was.) Sexsomnia sufferers need to make sure they don’t sleep near anyone with whom sexual touching would be inappropriate; they might even need to put an alarm on their bedroom door.

Also see that your sexsomnia client has mental health support. “Sexsomnia can decimate a person’s life in so many ways,” says James Olsen, the Bellevue mental health counselor and sex therapist. “It can directly cause harm to individuals they love and wish to protect while also damaging relationships, trust, and safety.” Often a key goal in psychotherapy is to reduce alcohol consumption, Olsen says, because drinking is frequently a trigger for an episode. 

When a person touches their child in a sexual way, as our client did, both child and parent likely need psychotherapy. Our client’s acquittal of child molestation was good news for him indeed. But even before the trial began, he was relieved to learn that his conduct did not mean he harbored a subconscious sexual desire for his daughter; it meant rather that he suffered a parasomnia whose worst manifestations could easily be controlled. 

When our client walked out of the courtroom a free man, his ordeal was over. But it had been a long and stressful process—his life had been largely on hold for the over two years it took to litigate the case. Thankfully, he was privileged enough to have made bail, unlike so many defendants. Ultimately, the case reminded us of a critical task of defense attorneys: to safeguard the rights of people with disorders like parasomnias as well as other health issues in a system that is often not well equipped to help them. 

About the authorS

Joshua Saunders is senior trial attorney at the Marshall Defense Firm, where his practice focuses on sex offenses, child abuse, and protection order cases. He is a graduate of NYU School of Law with years of experience in New York and Washington. He can be reached at:

David Marshall is the founder of the Marshall Defense Firm in Seattle. Since 1997, he has focused his practice on defense of persons accused of sex crimes, child abuse, and domestic violence—criminal defense in Washington, and civil defense in Washington and California. In his pro bono publico work, Marshall represented for eight years three prisoners at Guantanamo Bay. He can be reached at:


1. B. Bjorvatn, et al., “Prevalence of different parasomnias in the general population,” Sleep Med. (2010): 1031-4.

2. S. A. Chung, et al., “Frequency of sexsomnia in sleep clinic patients,” Sleep, no. 33 (2010): A226.

3. M. Anderson, et al., “Sexsomnia: Abnormal sexual behavior during sleep,” Elsevier Brain Research Reviews 56 (2007).

4. M. Ohayon, “Prevalence and comorbidity of nocturnal wandering in the U.S. adult general population,” Neurology 78 (2012): 1583-9.

5. Marco Tuccori, et al., “Neuropsychiatric adverse events associated with statins: epidemiology, pathophysiology, prevention and management,” CNS Drugs 28 (March 2014): 249-72.

6. Sleep medicine physician Clete Kushida sees one or two sexsomnia cases a month. About 10 percent of them come to him in connection with criminal prosecutions.