11/13/2015 14:33 EST | Updated 11/13/2016 00:12 EST

Closing arguments in first-degree murder trial of Guy Turcotte next week

SAINT-JEROME, Que. — The first-degree murder trial of Guy Turcotte has heard from its final witness.

Toxicologist and Crown expert Martin Laliberte was cross-examined by the defence today, concluding the presentation of evidence for both sides.

Final arguments are scheduled to start Tuesday beginning with the defence.

Turcotte has pleaded not guilty to two counts of first-degree murder in the stabbing deaths of his son, Olivier, 5, and his daughter Anne-Sophie, 3.

The ex-doctor has admitted to causing their deaths, but his lawyers argue the 43-year-old should be found not criminally responsible by way of mental disorder.

The accused testified he drank windshield washer fluid on Feb. 20, 2009, in order to kill himself and decided to murder his two young children to spare them the pain of finding his body.

Laliberte testified this week Turcotte would have only consumed windshield washer fluid about an hour before his arrest and suggested methanol, a toxic ingredient found in washer fluid, has minimal impact on the brain.

Defence lawyers tried to cast doubt on the reliability of Laliberte's conclusions by presenting scientific articles describing how the effects of methanol on a person can vary. 

(Cogeco Nouvelles)

The Canadian Press