Apparently monogamous sex gets tedious even when you’re tied up with rope.

Italian engineer Soter Mule, 42, and his girlfriend Paola Caputo, 24, were avid practitioners of Shibari, an ancient Japanese erotic art. More refined than your typical night of bondage, Shibari involves the use of thin pieces of rope to bind the submissive partner in ways that are meant to be both artistically beautiful and also heighten the sensation of his or her orgasm.

But last Saturday night, the couple was looking to spice things up even more. They met up with a friend of Caputo’s at a local pub in Rome and, after drinking heavily and smoking hashish, the three headed to the parking garage where Caputo worked as a daytime attendant. The dimly lit space was closed and desolate, the perfect setting for a kinky sex act. Mule strung the two women, with their consent and help, from a rafter with strategically placed soft ropes. He used their weight to counterbalance them, each with one foot on the ground. When one woman moved, it tightened the ropes and intensified the sensation for the other, and vice versa.

Everything was fine until the less-experienced woman fainted. The force of her sudden dead weight quickly lifted and strangled Caputo, even though Mule quickly tried to cut his girlfriend free. She died of asphyxiation, and the couple’s new friend nearly suffered the same fate. Mule was arrested and charged with involuntary manslaughter, and later released on house arrest.

In detailed testimony to the arraigning judge on Wednesday, Mule described how extreme sex like Shibari involves total control. He explained how he alternately teased and penetrated the women for maximum pleasure. He admitted that he made a mistake by not cutting Caputo from her bondage ropes sooner, but insisted that the extreme sex was consensual. “No one forced anyone,” he told the court. “Paola and her friend consented, but I was the master and I ultimately made the fatal mistake. I should have had the knife closer, as they suggest when practicing this type of bondage. By the time I found it, it was too late.”

When police searched Mule’s apartment, they found a cache of sex toys, bondage ropes, and albums of photos he had taken of women bound in various contortions. His computer was filled with content suggesting sexual deviancy or erotic artistry, depending on your point of view. Nothing Mule did was illegal. The surviving friend, still recovering in the hospital, backed up his version of events. There were no minors involved, and sadomasochism is not a crime in Italy.

Mule was an active member of several BDSM (bondage, discipline, submission, masochism) websites and posted frequently under the moniker Kinbaku, the name used for Shibari in the 15th century when its use was first recorded. Many of his followers looked to him for advice on how to practice Shibari. “He was considered an expert,” one friend of Mule’s told the ANSA news agency. “When practicing this kind of extreme sex everything has to be controlled, and he was well aware of that.”

Caputo’s death has since opened up a steamy debate in Italy, which has some of the highest numbers of extreme-sex aficionados in Europe, according to a poll by La Repubblica newspaper. Not to be confused with sexual predators who attack their victims, extreme-sex participants engage in risky, mutually consensual sex that they know could kill them if something goes wrong. One in 10 Italian couples practice “extreme sex,” which is defined as sex that could put one partner’s life at risk—and even those who aren’t doing things that could end in death are still risqué. Sixteen percent of Italian couples use masks and forms of bondage, and 5 percent admit to regularly engaging in mild sadomasochistic practices. Over half use erotic props in their usual sexual rapport. Just under 3 percent of the population has had sex with more than one person at a time, and slightly less than that have had group sex involving three or more partners.

Ayzad (he goes by only one name), author of A Guide to Extreme Eroticism published last year in Milan, told The Daily Beast that sexual extremism is a growing phenomenon across the globe primarily because of the Internet, which hosts thousands of websites and message boards where fetish fanatics can post their ideas and learn how to fulfill the most fringe erotic fantasies.

But the surge in high-risk sex has also led to an increase in accidental death when sex games go wrong. As many as 1,000 young men die each year of auto-erotic asphyxiation, or AEA, which is the practice of cutting off oxygen at the moment of orgasm to heighten the sensation. Michael Hutchence, the lead singer of INXS, allegedly died of an auto-erotic accident, as did Kung Fu star David Carradine. Only a few hundred women suffer the same fate. Many AEA deaths are called “suicide” since the victims are frequently found either hanging from a belt or rope or with a plastic bag over their heads. If a partner wasn’t involved, the victims are often found in the nude with pornography nearby.

But the real question is whether accidental death by orgasmic accident should be treated the same way as other accidental deaths. Every year there are hundreds of cases that make it to court. Last week a Swedish man was sentenced to 16 years in prison for “accidentally” killing a 17-year-old girl he met via the Internet. The girl had been strangled with a live electric cord during consensual sex. She had actually blogged about the thrill of the experience before the game turned fatal. In 2010, an Oklahoma man accidentally killed his wife when they were playing with a pistol during an erotic session. He was not charged with murder but instead convicted of a lesser crime. The year before, a Pennsylvania woman died of electroshock when her husband upped the amps on their “sex battery” which was wired to her nipples and vagina. He was charged with involuntary manslaughter but is already out of prison. In the U.K., a new law prohibits any citizen from possessing “extreme pornography” in the form of photographs from necrophilia to bestiality. Offenders can face prison time of up to two years and hefty fines. But the law stops short of making it a crime to engage in acts that could cause death to a participant.

“Accidents in extreme sex are rare,” says Ayzad. “You understand right away if it is for you or not.” And even if it is, that might not be enough to keep you alive.