Almost immediately after a police officer began interviewing three people accused of killing their family, he suspected they knew more than they were telling him, court heard Tuesday.

Tooba Mohammad Yahya, 41, her husband Mohammad Shafia, 58, and their son, Hamed Mohammad Shafia, 20, have each pleaded not guilty to four counts of first-degree murder.

Three teenage 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.

The family had stopped in Kingston, Ont., on their way home from a trip to Niagara Falls and they told police Zainab took the car keys after they stopped at a motel around 1:30 a.m. that night and that was the last they saw her.

"You mean that someone pushed them in?"

Court was shown videos Tuesday of police interviews with the family the day the bodies were found, and the detective is seen suggesting, especially to Hamed, that he may have witnessed something and isn't being truthful.

Det.-Const. Geoff Dempster confronts Hamed with the information that someone on a boat near the locks the night before heard a loud splash and also saw another large vehicle drive away.

"You mean that someone pushed them in?" Hamed asks.

Dempster says that's not what he was implying, but now, at the murder trial, that's exactly what the Crown alleges. The family is alleged to have used their Lexus SUV to push their Nissan Sentra, with the four victims inside, into the canal in the middle of the night.

The Nissan's back end was damaged, as was the front end of the Lexus, court has heard. The Crown alleges Hamed staged a collision with a pole in Montreal with the Lexus to account for the damage.

No explanation

Hamed's account of that collision is one of the many parts in his story that Dempster zeros in on, suggesting there are inconsistencies.

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The family is alleged to have used their Lexus SUV to push this Nissan Sentra into the canal in the middle of the night. (Trial evidence photo)

Dempster says he can't understand why, after the family had been driving non-stop from Niagara Falls since 6 p.m., the girls and women would want to hop into a car at 2 a.m.

"It's weird," he says. "No one here can make any sense of it. There's no explanation for them to be over there."

Dempster interviewed Hamed for a second time that evening after finding out Hamed had neglected to tell him about the damage to the Lexus.

Hamed appears at turns anxious and at turns bored in the interview.

"You know what, I'm telling you, I'm already in a lot of mess," Hamed says after Dempster confronts him about the Lexus collision.

"I don't know what you're doing, if you want to blame it on me. I don't know where you're going with this," he says.

Dempster excuses himself and leaves the room.

While he is gone, Hamed is seen biting his nail, cracking his knuckles, reorganizing cards in his wallet, reading through Dempster's notes and flexing his biceps.