KINGSTON, Ont. - Days before three teenage sisters from Montreal and their father's first wife were found dead in a car submerged in canal locks in eastern Ontario, someone was conducting searches on the family computer for tips on murder.

The Crown alleges the girls, and the woman who was like their surrogate mother, were killed by their parents and older brother because they thought the teens were dishonoring them by having boyfriends.

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.

They're charged in the deaths of Shafia daughters Zainab, 19, Sahar, 17, and Geeti, 13, as well as Rona Amir Mohammad, 50, Shafia's first wife who lived with the family in a polygamous relationship.

The Montreal family was on their way back from a trip to Niagara Falls, Ont., on June 30, 2009, when the bodies and sunken car were discovered at the bottom of a canal in Kingston, Ont. The accused staged the scene to look like an accident, the Crown alleges.

The months leading up to the deaths were not happy ones in the Shafia household, court has heard. Zainab ran away for a couple of weeks and the other two girls were contacting authorities, saying they wanted to be removed from the home because of violence, the Crown said in its opening statement.

Const. Derek Frawley, a Kingston police officer who analyzed the family laptop mostly used by Hamed, testified Thursday about searches of note that he came across.

They began on June 3, when Hamed and his father were in Dubai on business and most of the Google searches were routed through the United Arab Emirates' Google page, with queries about prisoners and "Montreal Jail," court heard. Several variations of "can a prisoner have control over his real estate" were searched, Frawley testified.

Then there were multiple searches for bodies of water, including one map time-stamped June 15 of the Kingston area, centred right on a road adjacent to the site where the deaths occurred, Frawley said.

Frawley also singled out searches for boat rentals in Montreal, various queries for metal boxes or "huge" boxes in Montreal and searches for visiting "Indian reserves."

On June 16 someone searched for "facts and documentaries on murders." Four days later someone searched "where to commit a murder." Ten days after that the three sisters and Rona Amir Mohammad were dead.

The cause of death for all four victims was drowning, but it isn't possible to say for certain that they drowned in the canal where they were found, the jury has heard. Three of them had bruising on the crowns of their heads. The jury has also heard testimony that despite the driver's window being open, it didn't appear as though anyone tried to escape the car as it was plunging into the water or after it was submerged.

Hamed's lawyer, Patrick McCann, suggested Thursday when cross-examining a witness from the day before that no one can say for sure how the "non-swimmers" would react in a panicked situation, teetering over the edge of the locks, then "water gushing through the window."