Shafia sisters
Shafia sistersCourt evidence

A Canadian jury on Sunday found a Montreal Muslim father, wife and son guilty of the first degree murder of the parents' three teenage daughters and a co-wife in the Muslim practice known as "honor killing."

After 15 hours of deliberations, the jury found Mohammad Shafia, 58; his wife Tooba, 42; and their son Hamed, 21, each guilty of four counts of first-degree murder. First-degree murder carries an automatic life sentence with no chance of parole for 25 years.

Prosecutors said the defendants, who are originally from Afghanistan, murdered the three teenage sisters because they felt they had dishonored the family by defying its rules on dress, dating and use of the Internet.

The judge described the crimes as "cold-blooded, shameful murders" resulting from a "twisted concept of honor."

The victims were Hamed's sisters Zainab, 19, Sahar 17, and Geeti, 13, as well as Rona Amir Mohammad, 52, Shafia's childless first wife in a polygamous marriage. Their bodies were found in the family’s Nissan, submerged in a lock on the Rideau Canal on June 30, 2009.

The prosecution convinced the court that the deaths were the result premeditated murder, staged to look like an accident after it was carried out. The murderers drowned their victims, then placed their bodies in the car and pushed it into the canal.

In a statement following the verdict, Canadian Justice Minister Rob Nicholson called honor killings a practice that is "barbaric and unacceptable in Canada."

According to CBC, the Shafias moved to Canada in 2007, having fled their native Afghanistan more than 15 years earlier. They had lived in Dubai and Australia before moving to Montreal and applying for citizenship. Mohammad Shafia was a prosperous business man who owned commercial property in the Montreal area and ran a business buying used cars in North America and shipping them overseas.

The court heard evidence showing that Rona had been unhappy in the marriage, while Zainab and Sahar, the two eldest daughters, had trouble with the strict household rules, which included a prohibition on relationships with boys. Both had secret boyfriends, wore fashionable clothes and resisted pressure from their parents and eldest brother to wear the hijab. Geeti was described as a rebel who also resisted her family’s rules.