They were members of a modern-day swingers' club in China, where people met online and then gathered in homes or hotels for group sex parties involving dozens of men and women.

Last month, Ma Yaohai, a 53-year-old college professor and 21 others went on trial in the southeastern city of Nanjing, accused of "group licentiousness" _ the first time anyone has been charged under a 1997 law in a case that has snagged huge public interest with its titillating details.

But aside from rampant curiosity in the swinger lifestyle, the uproar also has touched off a deeper debate about sexual freedom in a nation that is trying to reshape its own modern morality.

Ma said his decision to join the swingers was voluntary. "Marriage is like water. You have to drink it. Swinging is like a cup of wine. You can drink it if you like. If you don't like it, don't drink it," he said in interviews with Chinese media.

In arguing that his activities involved consenting adults meeting in nonpublic places, Ma's defiance seemed to strike a chord in an era of relative sexual freedom, where extramarital affairs and prostitution are common _ drawing support from those who believe the Chinese government should stay out of the bedroom.

Entering the court at the start of the two-day trial on April 7, he blurted out, "How can I disturb social order? What happens in my house is a private matter."

A verdict on Ma, the only member to plead innocent, is expected Thursday from the Qinhuai District People's Court in Nanjing, said his attorney, Yao Yongan. The charge carries a maximum sentence of five years in prison.

Ma was unavailable for comment because he is currently sequestered at his home, where he is caring for his elderly mother, under security surveillance, Yao said.

But in interviews ahead of his trial, Ma, who taught computer science at Nanjing University of Technology, declared his innocence: "I didn't do anything that hurt anybody else. I didn't force anyone else. Why is all the world focusing on me?"

Much of the public scrutiny has been on the lifestyle of "partner swapping," as it's known in Chinese. Newspapers have breathlessly noted the lurid details: The Internet chat room Ma set up for swingers was called "Traveling Couples," his personal sign-on was "bighornyfire," his orgies were sometimes held in the small apartment he shares with his Alzheimer's-stricken mother.

The twice-divorced college professor became interested in swinging in 2003 after his marriages failed. He initially joined chat rooms on the Internet and set up his own online group in 2007, Yao said.

Eventually, 200 people joined the group, organizing activities 35 times between 2007 and 2009, Yao quoted his client as saying. Ma himself participated in 18 sessions. Members decided on their own where to meet, Yao said. Among the 14 men and eight women arrested were white-collar workers, taxi drivers and salesclerks.

His trial highlights the vast social changes that China has undergone in the decades since it embraced economic reform. "Sex liberation stymied by law," trumpeted a front-page article in the official China Daily, which ran an in-depth piece that questioned whether China's laws on sexual behavior are lagging behind the times.

Chinese attitudes toward sex have changed dramatically during the last 20 years, said sociologist Li Yinhe, China's most prominent sex expert. Even a generation ago, holding hands and kissing in public were virtually unheard of. These days, studies indicate that 60 to 70 percent of Chinese have had sex before marriage, up from 15 percent in 1989.

"In the past, any sex activity outside marriage was unacceptable among people and could be punished," said Li, a member of the Chinese Academy of Social Sciences.

China used the so-called charge of "hooliganism," a catchall term that criminalized everything from premarital sex to dancing with members of the other sex and listening to Western music. During the early 1980s, a woman was sentenced to death for participating in secret dance parties, according to the China Daily.

But with rising prosperity and an easing of government controls on personal freedoms, China has shifted toward a more progressive view on sex, though attitudes remain much more traditional in the countryside than in urban centers. Sex motels cater to college students who rent by the hour, pornography is widely available on the Internet, and radio and TV shows devoted to sex advice are highly popular.

Even public views on the once-taboo topic of homosexuality have changed, Li said. Sodomy was decriminalized in 1997, while a survey she conducted two years ago found that 91 percent of people believe gays should not face discrimination in the workplace.

The immense growth of the Internet in China has played a factor in giving niche groups a space to operate, she said. The largest online site about group sex, Happy Village, has more than 380,000 registered members.

When Ma's case surfaced publicly, Li, along with other social commentators and academics, came to his defense. Though "partner-swapping" is against social norms, "just violating social convention isn't violating the law. As long as activities don't harm anyone else, one has a right to participate in them," she wrote in one blog post.

A prominent campaigner for sexual rights, Li even drafted a proposal to scrap the crime at the March session of the National People's Congress. It was submitted but no action was taken.

"Most people don't like Ma's activities. But most people also believe Ma should not be sentenced. People are more tolerant and they think that the authorities should not interfere in such things as long as it's not against someone's will," she said.

Ma has received some public backing. An online survey taken by Phoenix TV showed that 70 percent of 2,000 respondents believe he should be acquitted. A 2006 survey by the Institute on Sexuality and Gender showed that 40 percent of 6,000 respondents believed group sex should not be a crime, while most of the remainder felt it was immoral but that the penalties should not be so severe.

Even some of Ma's students have weighed in, posting their support on the popular Internet forum Tianya.

"We support him," wrote one student who identified himself as David. "How about those corrupt officials who secretly have mistresses? There are so many other issues in people's lives. Why don't (government officials) solve those instead of dwelling on this case?"

But others have been equally scathing in their criticism of what they view as a shocking crime. Group sex "should face a crackdown with a heavy hand. This case proves the law was necessary," wrote the Jiangsu Legal News, a Nanjing-based newspaper.

Regardless of the outcome, Yao said the case has challenged the government in highlighting the importance of individual privacy.

"I think because of this trial, many more people will realize the privacy issue. The case is about the government's invasion of privacy. It's about the protection of citizens' rights. People have the freedom to decide what to do with their body," Yao said.

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Associated Press researcher Xi Yue contributed to this report.