TORONTO -- A defence lawyer for Const. James Forcillo, who is facing murder charges in the death of an 18-year-old, is trying to show jurors that the police officer could have been closer to the teen than previously estimated.

Lawyer Lawrence Gridin pressed expert witness Eugenio Liscio today to use margins of error to estimate the distance between Forcillo and Sammy Yatim, who was shot dead on board an empty streetcar in July 2013.

Ultimately, Liscio came up with an "extreme" minimum of 2.66 metres from the tip of Yatim's knife blade to the officer's gun.

That's about a metre less than what he had previously testified was the likely distance using 3D computer modelling.

That means Yatim could have leapt off a streetcar and stabbed Forcillo within a second and a half, Gridin suggested.

Forcillo has pleaded not guilty to second-degree murder and attempted murder in Yatim's death.