KINGSTON, ONT. - Not only was a polygamist marriage normal for women in Afghanistan, Tooba Yayha told court that she operated within one in Canada.

In fact, the 41-year-old woman charged with murdering three of her children and the other woman in her marriage triangle says it worked quite well.

"If we did argue it would be for just five minutes and we would be laughing," she told the jury in Monday her first morning taking the stand in her defence.

With her husband Mohammad Shafia and son Hamad, she is charged in the shocking allegations of the honour killings of her three daughters Zainab, Sahar and Geeti and co-wife Rona Amir Mohammad. The four women's bodies were found in a car in 2009 in the Rideau Canal near here.

Defence counsel David Crowe is taking Tooba through her life with Shafia, which included an arranged marriage in Kabul when she was a teenager.

She said she agreed that her husband could marry a second wife, who also helped raise their seven children.

She also told the court how much the family missed Rona when they emigrated to Canada but thanks to slow paperwork had to leave her behind in Dubai and later in France for a total of five months.

Tooba said "we grew closer" when she finally came to Canada "because we missed each other."

She said when they did argue, "I would usually apologize because she was older."

Tooba also said she was unaware Rona was writing a diary of her life's experiences until she found a notebook after her death.

Her testimony continues.