Const. James Forcillo made a mistake in shooting Sammy Yatim, but that doesn't make him guilty of the charges he's facing, Ontario Superior Court Justice Edward Then said Tuesday in his final instructions to the jury.

Forcillo, 32, has pleaded not guilty to charges of second-degree murder and attempted murder in connection with Yatim's death on board a streetcar July 27, 2013.

On Tuesday, Then said the question jurors have to grapple with is not whether the 18-year-old posed a real threat "but rather whether Officer Forcillo reasonably believed in the circumstances that he was being threatened.

"Even if it was a mistaken belief, as long as it's reasonable, it can be justified," Then said.

He told jurors not to consider the Crown's opinion that police officers who testified had "circled the wagons" around Forcillo. He also warned jurors not to consider Yatim's state of mind at the time.

Yatim, who was high on drugs at the time, had frightened passengers on the 505 Dundas streetcar by exposing his genitals and then pulling out a knife.

The jury has heard evidence that Forcillo fired nine bullets at Yatim, eight of which struck the teen. The Toronto police constable said he was acting in self-defence.

Then hopes to leave Forcillo's fate in the hands of the jury by lunchtime Wednesday.

With files from Michelle Cheung