Columbia University professor David Epstein was charged last week with incest, accused of carrying on a three-year affair with his adult daughter.
According to the Columbia Spectator, the affair was consensual, but the political science teacher has been arraigned on one count of third-degree incest and could face up to four years in jail.
Epstein's lawyer, Matthew Galluzzo,
said that charges against his client were still "only allegations" that have not been proven.
"Academically, we are obviously all morally opposed to incest and rightfully so," he told ABCNews.com. "At the same time, there is an argument to be made in the Swiss case to let go what goes on privately in bedrooms."
"It's OK for homosexuals to do whatever they want in their own home," he said. "How is this so different? We have to figure out why some behavior is tolerated and some is not."
But he questioned why, if the alleged incest was consensual, why Epstein's daughter had been treated by prosecutors as "somehow a victim here, when she can be best described as an accomplice."
Incest is still socially and legally taboo in the United States, but attitudes may be changing in other parts of the world, at least when it involves adults and not minors.
Switzerland has proposed decriminalizing consensual sexual relationships between first-degree relatives, like siblings and also between parents and their adult children. Any coercive sex or incest with a minor would still be illegal.
Social conservatives in that country have called the bill "completely repugnant," and a survey has shown that 60 percent of the public opposes changing the law.
American psychologists and legal experts say that there are still sound reasons why incest should be illegal, even if it appears it is a choice between consenting adults.
"It is still a social taboo and the ick factor is much stronger than the criminal factor," said Professor Joanna L. Grossman, a professor of family law at Hofstra University in New York.
"I think these relationships are inherently coercive for the same reason that professors are not allowed to sleep with students in their classes," she said.
Consensual incest is legal in China, France, Israel, the Ivory Coast, the Netherlands, Russia, Spain and Turkey, according to a 2007 report from the Max Planck Institute in Germany.
The report was commissioned after a pair of siblings who had grown up separately but later reunited and had children.
Patrick S. was raised in an adoptive family and his younger sister Susan K. remained with their mother after a divorce. The pair met again in 2000 when he was 23 and she was 16 and moved back in with their mother. They subsequently fell in love and had four children.
Welfare authorities removed the three oldest children from their parents and Patrick was convicted of incest and was imprisoned for two and half years.
Mackenzie Phillips Confessed to Incest
Just last year in the United States, former child actress Mackenzie Phillips claimed that she had engaged in a decade-long consensual relationship with her father, the late rock star John Phillips.
She described in her book, "High Arrival," how incest fueled her drug use and mental health problems.
"No matter what kind of incest, it is an abuse of power," she wrote, "a betrayal of trust."
Robert Geffner, president of the Institute on Violence, Abuse and Trauma at Alliant University in San Diego, said there is no such thing as consensual incest because of the "power differential" in the parent-child relationship.
"The issue goes back to informed consent and power," he said. "You cannot have informed consent if the power relationship is already in existence."
"If you are saying consenting adults can do whatever they want, then what about therapists and their clients, employers and their employees, clergy and their parishioners?" asked Geffner.
Those who have been in incestuous relationships with a parent -- even as adults -- "mix up" power, love, affection, attention and abuse, he said.
Like Phillips, they can lose their identity, struggle with forming meaningful attachments and can resort to drugs, self-cutting and even suicide.
Laws against moral crimes like incest and bigamy were enacted in the "hey day" of the anti-vice movement in the earlier part of the 20th century, according to legal expert Grossman.
"Like bigamy, you can't marry and trying to do so is a crime," said Grossman. "There was a criminal code in every state and a lot of them were enforced."
But laws against crimes like adultery, co-habitation and fornication lost favor, and by the 1950s and 1960s, even states where they were on the books, did not enforce them.
In 2003, the Supreme Court struck down sodomy laws in Lawrence v. Texas, ruling that states could not criminalize "private, consensual, sexual or intimate conduct that does not involve minors or coercion," according to Grossman.
Most of those laws then disappeared, except for bigamy and incest, because they had "implications for the institution of marriage."
States have defended legal challenges to consensual incest with several compelling arguments.
"The scientific argument is that the state has an interest to protect the future offspring of an incestuous relationship who might suffer disproportionate genetic risks," said Grossman.
Anthropologists Margaret Mead and Claude Levi-Strauss argued that the incest taboo was "among the essential mechanisms of human society."
"You have to worry about how it changes the nature of the parent-child relationship," said Grossman. "If it's not taboo, and you end up dating or marrying your own daughter, it may corrupt the way you raise your children."
Incest Destroys the Family Relationship
If incest were not "absolutely off limits" in families, the natural affection -- sitting on laps and hugging and kissing -- would be compromised and unsafe, said Grossman.
"The state has an interest in protecting the welfare of children and the harmony of the family relationships," she said.
Families are also the "building blocks" of society, said Grossman. With incest, "you lose the possibility of a family connecting with another one and keeping society connected."
Meanwhile, Columbia's Epstein has taken an administrative leave, no longer teaching students, and preparing his defense.
As for the Swiss bill to lift the legal ban, it will not only have to pass Parliament, but a nationwide popular vote.
It will likely "take years to pass," if at all, according to Swiss journalist Urs Huber. "All the right wing, conservative parties have immediately protested against the idea."