TORONTO -- Testimony continues today at the trial of a man charged with murder in the death of a Toronto police officer who was run down by a snowplow two years ago.

Forty-six-year-old Richard Kachkar has pleaded not guilty to charges of first-degree murder and dangerous driving in Sgt. Ryan Russell's death.

On Wednesday, a fellow officer told the jury she found Russell dying on a snowy street after he was mowed down by the snowplow and cradled him.

Sgt. Sarah Andrews says she was on scene in about two minutes, but already Russell's breathing had nearly stopped and she couldn't find a pulse.

Witnesses say Russell tried in vain to stop the plow, backing away and firing shots at it in the seconds before it crashed into him, but it accelerated and drove directly at him. Russell was later pronounced dead that morning in hospital.

The judge has told the jury that there will be no dispute that Kachkar was the person driving the plow, rather the case will centre on his mental state.