The Shafia family murder trial wrapped up late Thursday in Kingston after a bomb threat delayed court proceedings earlier in the day.

In closing arguments, Crown attorney Laurie Lacelle said Mohammad Shafia, 58, his wife Tooba Yahya, 42, and their son Hamed, 21, were each responsible for planning and carrying out the murders of three Shafia sisters and Shafia's first wife from a polygamous marriage.

The evidence is "irrefutable," she said.

The bodies of Zainab, 19, Sahar, 17, Geeti, 13, and Rona Amir Mohammad, 52, were found June 30, 2009 in a car at the bottom of a canal in Kingston.

The Montreal family had stopped in the city the night before on their way home from a trip to Niagara Falls, Ont.

Each of the accused has pleaded not guilty to four counts of first-degree murder.

"Shafia, Tooba and Hamed had decided that there was a diseased limb on their family tree," Lacelle said. "Their decision was to trim the diseased limb and prune the tree back to the good wood."

"You know this was not an accident -- it was murder," Lacelle told the jury at the end of a long day. "They did what they each believed had to be done. Now it's your turn. Find them all guilty as charged. There is no other way."

Judge Robert Maranger will give the jury his final instructions Friday, and it's anticipated they will begin deliberating in the late afternoon.

The trial was delayed for several hours Thursday because of a bomb scare. Lawyers, staff, journalists and spectators were let back in shortly before 2 p.m., but under heavy security and screening.

Const. Steve Koopman couldn't say if the security threat was related to the Shafia trial.

"I cannot say 100 per cent, I think it's relatively coincidental that today Superior Court Justice Maranger was going to charge the jury and this is the most high-profile case in town," he said.

A source told The Canadian Press that a bomb threat prompted the evacuation.

The Crown has alleged that the Shafia girls were murdered by their father, his wife and their brother, and that the killing was then made to look like an accident after the fact.

The Crown's argument is built on the premise that the girls broke the family's moral code and dishonoured their family by wearing clothing that was not conservative and having secret boyfriends. Prosecutors said these were "honour killings."

The defence, however, calls the argument preposterous and said the deaths were the result of a tragic accident.

With files from The Canadian Press