SAINT-JEROME, – Guy Turcotte’s lawyers questioned a final Crown witness at length on methanol and its effects during a technical cross-examination Thursday.

Toxicologist Martin Laliberte was questioned much of the afternoon over testimony that often sounded like an advanced course on toxic chemicals and drugs.

The case was put on hold briefly by Quebec Superior Court Justice Andre Vincent on Thursday to allow defence lawyer Pierre Poupart time to prepare a cross-examination.

The cross-examination of the final witness will now spill into Friday.

Laliberte testified Wednesday that 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.

Armed with scientific literature, the defence attempted to demonstrate that those health effects can vary greatly from person to person.

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 the fluid on Feb. 20, 2009 to take his own life and decided to also kill his two young children to spare them the pain of finding his body the next day.

(Cogeco Nouvelles/The Canadian Press)