KINGSTON, Ont. -- Mohammad Shafia tried to enlist a family member in a plot to drown his eldest daughter, Zainab, just one month before her body was found in a submerged car in the Rideau Canal in 2009, court heard Tuesday.

The startling testimony came at the Kingston Mills murder trial in which Shafia, his wife, Tooba Mohammad Yahya, and their son, Hamed, each stand accused of four counts of first-degree murder.

The witness, who can't be identified because of a publication ban, said he also warned Tooba about her husband's intentions.

"I told her Shafia wanted to kill Zainab - to drown her. If he wants to take her on a trip, don't accept," he testified.

It was while the Shafia family was returning from a family vacation in Niagara Falls in the early hours of June 30, 2009, that they stopped in Kingston.

At around 8:30 that morning, a black Nissan Sentra owned by the Shafias was found underwater at the top of the Kingston Mills locks with four bodies inside - those of Zainab, 19, two of her younger sisters, Sahar, 17, and Geeti, 13, as well as that of Rona Amir Mohammad, Shafia's first wife.

The witness said he initially called Mohammad Shafia in Dubai to help the family sort out clashes they were having with Zainab. It was then that Shafia tried to enlist him "to fulfill the murder plan of Zainab," he alleged.

Under examination by Crown attorney Gerard Laarhuis, and through an interpreter, the family member recalled what Shafia had told him about the ongoing clashes with Zainab, and said he used strong language to describe Zainab.

Shafia's lawyer, Peter Kemp, was only one of the three defence attorneys who had time to cross-examine the witness Tuesday.

Kemp asked the man why he didn't contact Montreal police directly when he learned of the plot instead of calling other family members. And said he also found it puzzling that the man would have been enlisted by Shafia in a murder plot when they had had a falling out a number of years before and never spoke to one another.