The trial of a Montreal couple and their son who are accused of killing three sisters and a woman was postponed Thursday until next week in Kingston, Ont., because of a medical emergency involving the father, according to police.

The delay in the trial of Tooba Mohammad Yahya, 41, her husband, Mohammad Shafia, 58, and their son, Hamed Mohammad Shafia, 20, comes during a week in which the court has been hearing dramatic video of the accused under police interrogation.

They have each pleaded not guilty to four counts of first-degree murder.

Mohammad Shafia was not with his wife and son as usual when officials led the two accused into the courtroom Thursday.

Shafia was not taken to Kingston General Hospital on Wednesday night as earlier published, but to the Lennox and Addington County General Hospital in nearby Napanee. He was being transferred to Kingston General Hospital on Thursday as a result of a fairly serious medical emergency, police said.

Although the judge did not specify which family member had taken ill, resulting in the trial's postponement, police later confirmed it was the elder Shafia.

It's unclear when the trial will resume, but the judge told the jury he would update them by next Wednesday.

The Shafia sisters, Zainab, 19, Sahar, 17, and Geeti, 13, along with Shafia's other wife, Rona Amir Mohammad, 50, were found dead inside a submerged car in June 2009 in the Rideau Canal.

Mohammad was one of Shafia's two wives in a polygamous marriage.

On Wednesday, Yahya told police in the video that she was not aware the father of her children was going to kill their girls.

The interrogation shows Yahya crying and appearing worn out, as a police officer asks her questions about the night in June 2009 when the four were found dead.