An "honour killing" expert at the Shafia quadruple-murder trial in Kingston, Ont., has told the courtroom that in some cultures honour is valued above human life.

University of Toronto professor Shahrzad Mojab testified Monday at the canal deaths trial, where a husband, wife and son face murder charges in the deaths of four family members.

Mohammad Shafia, 58, an Afghan businessman, his wife Tooba Yahya, 41, and their son Hamed, 20, are accused of killing four female family members. All of them have pleaded not guilty to four counts each of first-degree murder.

Three of the Shafia sisters – Sahar, 17, Zainab, 19, and Geeti, 13 – along with Mohammed Shafia's first wife, Rona Amir Mohammad, were found dead in a car found submerged in a canal, outside Kingston.

Mojab told the jury trial that in certain cultures, the notion of family honour is linked to female sexuality, and the capacity to control it.

This belief is seen predominantly in the Middle East, Mojab said.

When family honour is threatened, it is acceptable and expected that a male family member could kill a relative.

Mojab is among the Crown's final witnesses at the Shafia trial.

Prosecutors allege Shafia, his second wife Tooba and their son Hamed killed Sahar, Zainab, Geeti and Rona because they dishonoured their family by having boyfriends and living a modern lifestyle.