SAINT-JEROME, Que. -- The concentration of methanol in Guy Turcotte's blood was the equivalent of between three and five beers for an average-sized man, a defence witness told his first-degree murder trial Thursday.

The same witness, toxicologist Anne-Marie Faucher, testified Wednesday she found a potentially fatal dose of methanol in Turcotte's system the day after the February 2009 slayings of Olivier, 5, and Anne-Sophie, 3.

Turcotte, 43, has pleaded not guilty to two charges of first-degree murder but has admitted to causing the children's deaths.

His lawyers are arguing he should be found not criminally responsible by way of mental disorder.

The accused testified this week he was determined to die and that he consumed windshield washer fluid, which contains methanol. He said he could only remember the night of the slayings in "flashes."

Under cross-examination by the Crown Thursday, Faucher said she estimates someone who has consumed that much beer is "conscious, coherent, able to have discussions and negotiate."

Faucher said such a person "is quite capable of doing what he has to do," but had noted in her initial testimony one's level of awareness can be reduced after consuming such levels of methanol.

She explained that the effects of methanol on the human body are similar to those from the consumption of ethanol (the alcohol found in wine or beer), but have less of an impact.

Prosecutor Rene Verret questioned her experience on methanol intoxication, with Faucher replying she has worked only on three or four similar cases and that the only survivor was Turcotte.

Evidence presented thus far has not established the quantity of washer fluid he consumed.

Later on Thursday, Claude Rouillard, an expert in neuropharmacology, said methanol does result in memory loss.

He referred to a scientific article regarding a mass poisoning in New York in 1953 where people had been drinking a mix of fake whisky and methyl alcohol (or methanol).

Several people ended up going to hospital to be treated and had suffered major memory loss. Some couldn't recall setting foot in the hospital or how they got there, but they appeared rational when observed by medical personnel.

The Crown asserts that Turcotte has a "selective memory" when it comes to the events of Feb. 20, 2009.

Rouillard's testimony continues Friday.