QUEBEC CITY -- The Crown's cross-examination of an expert witness in the case of the Quebec City Halloween 2020 murders led to tense exchanges on Monday between the judge and the prosecutor.

Prosecutor Francois Godin suggested that Dr. Gilles Chamberland, a forensic psychiatrist testifying for the defence, was biased and had a preconceived notion about the accused before he was asked to evaluate him.

It was a comment that earned the Crown a rebuke from the trial judge for making "vexatious" remarks.

"Show him a minimal amount of respect," Quebec Superior Court Justice Richard Grenier told Godin.

An 11-person jury must determine if Carl Girouard is criminally responsible for killing two people with a sword and injuring five others on Oct. 31, 2020. Girouard, 26, is accused of two counts of first-degree murder and five counts of attempted murder and has admitted to the physical acts. He maintains he was not criminally responsible because he suffered from a mental disorder.

The Crown argues that Girouard was able to distinguish right from wrong when he stalked the streets of Old Quebec on Oct. 31, 2020.

Chamberland has testified that Girouard likely suffered from schizophrenia and was in a state of delirium when the attacks took place. Nothing other than mental illness, he said, could explain the killings, noting that the accused had responded well to medication.

The doctor, who often gives media interviews, had gone on the radio the day following the murders and said Girouard suffered from a mental disorder.

Godin asked the doctor in court on Monday whether he was familiar with the concept of "hypothesis confirmation bias."

"No matter what we will be confronted with, we will look for elements to confirm our hypothesis," Godin said to the witness.

The judge said he didn't take issue with Chamberland's radio interview during which the doctor said the accused had a mental illness.

"Any psychiatrist who was asked the question would have answered that -- come on!" Grenier said, adding that the doctor didn't equate mental illness with the legal defence of not criminally responsible.

Earlier on Monday, Chamberland told jurors that Girouard was not considered dangerous enough before the killings to be forced into treatment.

Chamberland says that was the case for Girouard despite the fact the accused had openly told health professionals six years before the murders that he wanted to use a sword to kill people.

The witness said police would have needed to believe there was a serious and immediate danger to arrest Girouard, adding that the danger involving the suspect was unclear.

-- This report by The Canadian Press was first published on May 2, 2022