A young man accused of killing his three sisters and the first of his father's two wives may have been "stupid" and "morally blameworthy," but he is not guilty of murder, his lawyer told court Wednesday.

Hamed Shafia, 21, and his parents Mohammad Shafia, 58, and Tooba Yahya, 42, are on trial for four counts each of first-degree murder. They have pleaded not guilty.

"Hamed is guilty of being stupid, morally blameworthy, but other than that, he was not responsible for the girls' death, nor were his parents and (it's) time to put an end to this Kafkaesque 2 1/2 years they've been going through since their arrest," Hamed's lawyer Patrick McCann told the jury in his closing statement.

McCann told the jury the only reasonable conclusion they can come to is that the deaths of sisters Zainab, 19, Sahar, 17, and Geeti, 13, as well as Rona Amir Mohammad, 52, were a tragic accident witnessed by his client.

The four bodies were found June 30, 2009, in a car submerged at the bottom of the locks of a canal in Kingston, Ont., where the Montreal family had stopped on their way home from a trip to Niagara Falls.

Shafia, Yahya and Hamed all told police that Zainab had borrowed the car keys and likely went on an ill-fated joy ride with the other three. Zainab did not have a driver's licence and was an inexperienced driver, so the car must have accidentally ended up in the canal, her parents told police.

In a recorded conversation with an interpreter who was really a private investigator four months after the Shafia family's arrest, Hamed admitted he was there when the car went into the canal. He said he had followed his sisters and Mohammad out of concern and rear-ended them near the scene.

While he was picking up pieces of a shattered headlight, Hamed told the investigator he heard a splash and ran to the edge of the canal. He said he called his relatives' names and dangled a rope in the water, but there was no response. He left and drove through the night home to Montreal without calling police.

Hamed's decision not to call 911 was "terrible," his lawyer said, but he was scared. The Crown called Hamed's story a "complete fabrication."

In the beginning of her closing arguments Wednesday, Crown attorney Laurie Lacelle also said Hamed's story doesn't explain why the seats in the submerged car were reclined all the way. It would be odd if Zainab was driving like that, she said.

Lacelle suggested instead that the victims were reclined and sleeping in the car when they were killed.

"After murdering four individuals, Shafia, Tooba and Hamed could hardly be expected to re-adjust the seats to accord with the accidental driving mishap that they wanted to use to explain the deaths," Lacelle told the jury. "It's just one more detail they didn't think about."

The lawyers for all three accused have bristled at the Crown's theory that the women's deaths were honour killings because their behaviour had shamed the Shafia family.

During the trial, the court heard from teachers, child protection workers and police about reports from the girls that they were afraid of their father and brother and either had wanted to leave the family home or had tried to run away.

McCann described the evidence the women gave to authorities as unreliable and suggested that they had a penchant for lying. He said the evidence is indicative of ordinary teen rebellion and isn't a motive for murder.

He called the suggestion of an honour killing "preposterous."

The lawyers for Shafia and Yahya insisted the Crown had not only failed to adequately explain how the women died, it also failed to prove its honour killing theory.

The Crown is expected to wrap up its closing argument Thursday. That will leave the judge to instruct the jury Thursday and Friday. The instruction is expected to take almost two days, because the judge will need to carefully explain the law to the seven-woman, five-man jury and present them with their options.

While it's been a long trial, with 10 weeks of testimony from 58 witnesses, CTV's Genevieve Beauchemin says the jury members are doing their best to stay focused during these final days.

"They're listening to every word that the defence lawyers are putting to them," she told CTV's Canada AM Wednesday from Kingston.

Shafia's lawyer, Peter Kemp, said despite weeks of testimony and considerable evidence, the Crown left too many unanswered questions for the jury to reach a guilty verdict.

"The Crown's theory is that they were already dead or unconscious when they were put in the locks, and so all the drowning did, if they drowned in the locks, is finish it off, they were killed somewhere else," he said.

"Where? Why? How?"

Kemp laid out a possible murder scenario that had Shafia taking each woman from the car one at a time, drowning them, hiding their bodies until he was finished and then moving the bodies back to the car and pushing it into the canal.

Kemp said that scenario was unrealistic and there was not enough time for Shafia to follow through on such an elaborate act.

Yahya and Shafia have refuted all of the Crown's evidence, insisting there was not way they would have ever killed their own children.

They both testified that they knew nothing of what happened that night, though Yahya was forced to admit she had initially lied to police when she said she and the two Shafia men had been at the canal that night.

--With files from The Canadian Press, CTVNews.ca's Andrea Janus and Angela Mulholland