As many as 5,000 women and girls lose their lives — most at the hands of family members — in "honour killings" around the world each year, according to the United Nations.

Up to a dozen have died for the same reason in Canada in the last decade, and it's happening more often, says Amin Muhammad, a psychiatrist who studies honour killings at Memorial University in Newfoundland.

"There are a number of organizations which don't accept the idea of honour killing; they say it's a Western-propagated myth by the media, but it's not true," he says. "Honour killing is there, and we should acknowledge it, and Canada should take it seriously."

Kingston, Ont., police are now investigating that as a motive in the deaths of three teenage sisters and an older female relative who were found in a car submerged in the Rideau Canal in Kingston on June 30. The girls' mother, father and brother were arrested on Wednesday and charged with first-degree murder.

"In our Canadian society, we value the cultural values of everyone that makes up this great country, and some of us have different core beliefs, different family values, different sets of rules," Kingston Police Chief Stephen Tanner said at a news conference on Thursday. "Certainly, these individuals — in particular, the three teenagers — were Canadian teenagers who have all the freedom and rights of expression of all Canadians."

He added that he'd received an e-mail from an extended family member of the girls, suggesting honour killing was to blame for their deaths.

Honour killings can be sparked by a woman talking to a man, having a boyfriend, wearing makeup or revealing clothing, or even seeking a divorce, says Diana Nammi, founder of the London-based International Campaign Against Honour Killings. Nammi, originally from Iran, says children of immigrants who grow up in western nations take those freedoms for granted, which can throw them into conflict with their parents' rigid standards.

"When people are moving to another country, they leave everything they have, all their possessions, behind. But what they can bring with them is what they believe, their culture, their traditions, their religion," she says. "Unfortunately, they are choosing to show the worst part of that, and the worst and criminal part of that is controlling women."

One of the earliest honour killings involving a Canadian occurred in 2000, when Maple Ridge, B.C., resident Jaswinder Sidhu was murdered in India in what police called a contract killing, after she married a man she met while travelling.

In 2003, Amandeep Atwal, 17, died after her father stabbed her 17 times. The Kitimat, B.C., teen had been secretly seeing a boyfriend.

Sixteen-year-old Aqsa Parvez's father and brother are currently awaiting trial for her strangulation death in 2007, and friends said the Brampton, Ont., teen had been clashing with her family over her refusal to wear the hijab.

In May, an Ottawa man was sentenced to life in prison for killing his sister, Khatera Sadiqi, 20, and her fiance.

"We cannot say there's a huge number of cases, but now the cases are increasing, and very soon we'll have a problem in Canada," says Muhammad.

Men occasionally die in honour killings, he says, but young women are almost always the victims in western countries.

Honour killing is most prevalent in nations with large Muslim populations, but Aysan Sev'er, a professor of sociology at University of Toronto Scarborough and author of an upcoming book on the subject, says there's nothing in Islam that sanctions the practice. Some perpetrators use religion as a "cloak," she says, but honour killing is about patriarchy, not religion.

"A few women are really sacrificed to terrorize all women, to push them into submission, where they are not in the position to defend themselves or even their daughters or sisters," Sev'er says.

It's wrong-headed to blame particular cultures or further stereotype the Middle East, she emphasizes, but Canada cannot overlook the motivation for these "heinous crimes."

"In Canada, we have been extremely culturally sensitive, and that's a good thing," she says. "But in this particular case, we may have pushed the pendulum a little to the other side, in the sense that there are cultural components in these types of crimes which we cannot ignore."