The lawyer representing Mohammad Shafia, one of three Montrealers accused of pushing four family members into the Rideau Canal and killing them, said on Tuesday there are too many unanswered questions about the case to convict his client of murder.

"With all these unknowns, it's only speculation that can provide answers, and speculation is not proof beyond reasonable doubt," Peter Kemp said, addressing the jury in his final submission to the court.

Shafia, 59, Tooba Yahya, 42, and their eldest son, Hamed, 21, are each accused of four counts of first-degree murder in the deaths of three Shafia sisters and their father's first wife in a polygamous marriage.

Zainab, 19, Sahar, 17 and Geeti Shafia, 13, along with Rona Amir, 52, were found drowned in a submerged car in the Kingston Mills lock in eastern Ontario in June 2009.

Kemp focused on the timeline, saying the time it would take to individually drown the four victims, place their bodies into the Nissan, push it into the lock and then drop off Tooba and Shafia at the motel doesn't fit with the evidence presented.

Kemp said the process of killing the four women would take at least 117 minutes. He detailed the process and asked the jury to think of it like a "motion picture" playing out.

Peter Kemp addressed the jury in his final submission to the court. (Mike McLaughlin)

The time between when Shafia and Hamed were seen at the Kingston East Motel, just before 2:30 a.m., and when Hamed's cellphone activity was captured on a cell tower in Montreal, at 6:48 a.m. just doesn't leave enough time for a murder, he said.

"There was no time in that scenario for a murder to take place," Kemp said.

One of the more challenging aspects for the prosecution in the case has been the lack of physical evidence linking the accused to the crime, as well as proving to the jury that a crime took place.

An autopsy showed the women drowned, but the coroner could not specify where they drowned or if they were dead before the car went into the water.

The Crown's theory was that the women were either dead or unconscious when they were placed in the Nissan and pushed into the water by the family's Lexus SUV. Pieces of the SUV's headlights were found at the scene.

But Kemp asked the jury to consider how it would be possible to drown four people one-by-one without the other victims knowing or running away, and without leaving any sign of a struggle.

"The problems would have been almost insurmountable," Kemp told the jury, detailing that the accused would have had to lure each victim out of the Nissan separately, drown each one without alerting the others or anyone sleeping in boats moored nearby, carry each body back up a hill from the nearby pond and put each one back in the car.

Motive questioned

Kemp also addressed the motive presented by the Crown: that the women were killed to restore the family's honour. "Honour killings are not permitted in Islam," he told the jury.

"If you comb through the Qur'an, you would not find a single passage that advocates honour killing … but, there are plenty of prohibitions against murder."

Earlier, Kemp, addressing evidence given by teachers, child protection officials, family members and other witnesses, said there is no proof in any of the testimony that Shafia's daughters and his first wife were abused or in imminent danger.

"The people who said the children and Rona are in danger … none of these people apparently were concerned enough to call the police," Kemp told the jury. "The allegations that were made may very well have been made in hindsight, to look back at what caused the events that occurred on June 30, 2009."

Kemp said the Shafia family themselves involved police in domestic matters on more than one occasion.

Hamed and Shafia called police when daughter Zainab ran away to a women's shelter in April 2009, Kemp said. A surviving Shafia child also called police when Zainab ran away, worried about their father's reaction, Kemp said.

The children said there was no danger and they were simply angry at their father because he caused Zainab to run away, Kemp said.

The children weren't removed from the home even though children's services attended, Kemp said.

The Crown alleges the defendants killed the women because Sahar and Zainab Shafia were thought to have dishonoured the family by having boyfriends and living a modern lifestyle. The defence maintains that the deaths were an accident, which occurred after eldest daughter Zainab took the keys to the family's Nissan sedan and embarked on a joyride with her sisters and Amir.

Kemp told the jury there was no issue between his client and the eldest daughter Zainab before the family went on a trip to Niagara Falls. The deaths occurred during the family's return journey.

Shafia had forgiven his daughter for her failed marriage and for running away to a women's shelter, Kemp said. She had agreed to marry another man approved of by the family and she was happy, Kemp said.

"I respectfully suggest to you that at the point that the family departed to go to Niagara Falls, Zainab's transgressions had been forgiven," he said.

Kemp referred to Amir's diary, in which she alleged she was beaten and ostracized by the family and lived a lonely life with the Shafia family.

Tooba Yahya's lawyer David Crowe focused heavily on the testimony of an honour killing expert who was called by the prosecution. (Melinda Dalton/CBC News)

Kemp showed the jury photos of Amir and Sahar, taken shortly before their deaths, and suggested there was no evidence given that proved Amir was abused or unhappy.

Honour killing expert

Yahya's lawyer, David Crowe, focused heavily on the testimony of an honour killing expert who was called by the prosecution.

Crowe said the accused all came from prosperous families, valued education and do not fit the profile described by the expert.

The defence lawyer pointed out that the expert testified that the reaction to honour killings both inside and outside Afghanistan is outrage.

He asked the jury how outrage would equate to restoration of honour.