A 44-year-old drifter was in a psychotic state when he stole a snowplow and used it to kill a Toronto police officer and should be found not criminally responsible, a jury was told Tuesday.

There is "no doubt" Richard Kachkar was driving a stolen plow on Jan. 12, 2011, when it hit and killed Sgt. Ryan Russell, Ontario Superior Court Judge Ian MacDonnell told the jury trying Kachkar's case. What jurors must decide is whether Kachkar knew what he was doing was wrong.

The Crown, which wrapped up its case Tuesday after three weeks of evidence, contends Kachkar meant to kill Russell and should be found guilty of first-degree murder.

Kachkar's lawyer, Bob Richardson, began his case by telling the jury he is raising a defence of not criminally responsible.

"It is our position that Mr. Kachkar...was suffering from a mental disorder the entire time that he was operating that snowplow," Richardson said.

Richardson has conceded that if the jury does believe Kachkar is criminally responsible, he is at least guilty of manslaughter.

Three psychiatrists who assessed Kachkar in the lead-up to his trial, including one selected by the Crown, each concluded that Kachkar was suffering from a mental disorder at the time he was operating the plow — a "psychotic state," Richardson said.

Plow stolen while Kachkar barefoot

Court has heard that Kachkar was not wearing socks, shoes or a jacket on the snowy January morning when he stole a truck with a plow attached on the front from two landscapers who had stopped for a coffee.

He drove the plow through the streets of Toronto for two hours early that morning, crashing into other cars, crossing into oncoming traffic and going through red lights, witnesses have testified.

Russell had tried to stop Kachkar about an hour after he had commandeered the plow. After Russell got out of his cruiser, Kachkar drove the plow straight at the officer, knocking him to the ground and fracturing his skull, court has heard.

At various points Kachkar was yelling about Chinese technology, "Russian Facebook" and paramedics putting microchips in his body, court has heard.

The rampage only ended after he hit a garbage truck and was cornered by emergency task force officers who Tasered him three times and shot him twice, witnesses testified.

Richardson told the jury they don't have to be concerned with the penalties no matter their decision, but he said if they find Kachkar not criminally responsible it doesn't mean he will walk free.

Kachkar is also charged with dangerous driving, but the judge told the jury they no longer have to consider that charge.

Adopted shortly after birth, Kachkar has had no contact with his biological parents, but the detective in charge of investigating Russell's death managed to track down Kachkar's biological father, who likely has a mental illness, Richardson said.

The defence intends to read a statement from Kachkar's birth father to jurors.

Kachkar spent time in shelter

Kachkar had been staying at a shelter in St. Catharines, Ont., feeling estranged from his wife and two children, witnesses have testified, and came to Toronto in early January to stay at a friend's house.

The friend, Steve Brown, testified Tuesday that during that period Kachkar was acting strangely. He abruptly left Brown's apartment the day before Russell's death, court heard.

He went to a walk-in clinic, where he said he was scared but didn't know why, a receptionist testified Tuesday.

The doctor who examined Kachkar that day, Raphael Odhiambo, also testified in court on Tuesday.

Odhiambo said Kachkar then told him that he hadn’t slept in days.

He told the court that at the end of his meeting with Kachkar: “I felt he had a mental illness.”

Odhiambo suggested that Kachkar go to an emergency room or to the Centre for Addiction and Mental Health.

He said Kachkar kept repeating that he was scared. But under cross-examination, Odhiambo said that he didn’t appear dangerous and seemed competent.

Court has previously heard Kachkar then went to a shelter in Toronto where he spent the night before stealing the snow plow. He told workers there he was afraid he was going to do something bad, court has heard.

Richardson expects to call several witnesses, including the three psychiatrists, over the next few weeks.

The judge told the jury that although accused people are presumed innocent until the Crown proves them guilty beyond a reasonable doubt, the onus shifts in the case of not criminally responsible defences.

A person is presumed to be criminally responsible and whoever raises the issue, the defence, has the burden of proving the accused are not criminally responsible, MacDonnell said.

The trial continues on Wednesday.

With a report from the CBC's Steven D'Souza