Few phrases in the popular discourse are as contentious as "honour killing," but the recent murder trial of a family of Afghan immigrants convicted of killing four female relatives has forced Canadians to once again grapple with this controversial issue.

Mohammad Shafia, his wife, Tooba Yahya, and their son, Hamed, were found guilty of first degree murder in the death of Shafia and Yahya's three teenage daughters and Shafia's first wife, Rona Amir Mohammad. They were sentenced in a Kingston, Ont., courtroom on Jan. 29, 2012, to life in prison with no possibility of parole for 25 years.

During the course of the three-month trial the Crown successfully argued that Mohammad, 50, and sisters Zainab, 19, Sahar,17, and Geeti, 13, were killed because Sahar and Zainab were thought to have dishonoured the family by having boyfriends and living a modern lifestyle.

Their bodies were found in a submerged car in the Rideau Canal near Kingston in 2009.

In a wiretapped conversation between Shafia and his wife and son after the bodies were discovered, Shafia revealed his anger at seeing suggestive cellphone photos of his two eldest daughters: "Curse God on both of them. Is that what a daughter should be? Would a daughter be such a whore?"

When handing down his sentence, Ontario Superior Court Judge Robert Maranger called the crimes "despicable" and "heinous" and said:

"The apparent reason behind these cold-blooded, shameful murders was that the four completely innocent victims offended your completely twisted concept of honour … that has absolutely no place in any civilized society."

Though often linked to sexual issues such as adultery and premarital sex, the perceived "offences" that have prompted honour killings have come to include a woman's push for independence.

To some observers, honour killings confuse the issue of domestic abuse with religious connotations. For others, it's an important designation of a cultural phenomenon distinct from domestic violence.

Global problem

There are documented cases of men being killed for ruining a family's reputation, but the vast majority of the victims are female.

Believed to have originated as a patriarchal tribal custom, honour killings are a global phenomenon. A 2000 report by the UN Population Fund estimated that as many as 5,000 women and girls are killed each year by relatives for allegedly dishonouring their family.

A 10-month investigation by Britain's Independent newspaper in 2010, however, said woman's groups in the Middle East and Southwest Asia peg the figure at closer to 20,000.

Shahrzad Mojab, a professor of women's studies at the University of Toronto, was called in on Dec. 5 as an expert witness in the Shafia trial. She told the court the rationale behind honour killings is a belief that "the shedding of the blood is a way of purifying the name of the family."

While the practice is often associated with Muslim cultures, it also happens among Christians, Hindus and Sikhs. The Independent story suggested the practice is strongest in Pakistan and Turkey, as well as among Palestinians in Jordan and Kurds in northern Iraq.

Due to immigration, the issue has become a growing concern in countries like the U.S., Britain and Canada.

Canadian cases

A number of domestic cases have recently made the headlines in Canada.

In 2010, Muhammad Parvez and his son Waqas were sentenced to life imprisonment for the murder of 16-year-old Aqsa Parvez, who had been found strangled in her family's Mississauga, Ont. home in 2007.

The killing is believed to have been the result of arguments Parvez had with her father about wearing a traditional hijab.

In 2006, 20-year-old Khatera Sadiqi and her fiancé were shot to death outside an Ottawa shopping plaza. Her brother was found guilty of the murder, having told the court he wanted his sister to respect their father.

The issue has become so pressing that the study guide for the Canadian citizenship test refers to it explicitly, saying that "Canada's openness and generosity do not extend to barbaric cultural practices that tolerate spousal abuse, 'honour killings,' female genital mutilation, forced marriage or other gender-based violence."

In a 2009 edition of the U.S. policy journal Middle East Quarterly, American feminist writer Phyllis Chesler argued that honour killings are distinct from domestic violence. (The journal is published by Middle East Forum, the think tank of controversial U.S. scholar Daniel Pipes. The forum lists its mission as promoting American interests in the Middle East, which in its view include "fighting radical Islam.")

According to Chesler, honour killings differ from domestic abuse because they are planned in advance and often rely on collusion between multiple family members.

Gender inequality

Other observers think the problem is rooted in inequality. Writing in the Huffington Post, John L. Esposito, professor of religion and international affairs at Georgetown University, said that linking honour killings to a religion like Islam misses an opportunity "to address what is truly intolerable: gender-based violence."

While there is much debate over the suitability of the term honour killing, legal experts say that it shouldn't cloud the issue of culpability.

"I think we need to be careful not to allow social phenomena to change our response in terms of the criminal justice system," says Carissima Mathen, a professor of law at the University of Ottawa.

"Ultimately, motive doesn't make you more or less guilty. Planned and deliberate murder is a crime that is equally serious, no matter what the circumstances."

Mathen doesn't believe Canada's Criminal Code should be modified to accommodate this emerging problem.

"I would not expend resources on crafting special criminal laws to deal with this offense," Mathen says. "I would put the focus on prevention, education and outreach."

With files from Amber Hildebrandt and Canadian Press