a long chain around the shooter’s neck, a medallion and chain
just like those seized from the appellant on arrest. The defence
argued otherwise: the white object was a reflection from the collar of the white t-shirt underneath the outer shirt. It was not
a medallion because, despite the struggle with Grant, the object
did not appear to move between frames of the video as a medallion like that seized from the appellant would have done.
The proposed evidence
 In support of its characterization of the white object, the
defence proposed to elicit expert opinion evidence from Dr. Jason
Harlow, a senior lecturer in physics at the University of Toronto.
The trial judge heard the proposed testimony on a voir dire.
 Dr. Harlow explained that a large area of his research
involved the study of light, including observations on the movement of objects on camera, particularly of objects that may reflect
light. He analyzed several video frames to determine whether
a white area below the shooter’s head could be light reflected
from a medallion on a long chain. Dr. Harlow concluded that although it was possible that the white spot apparent in the video
was the chain and medallion, it was unlikely to be so.
 The analysis Dr. Harlow conducted was grounded entirely
on his visual observation that the white spot did not move
between two frames of the video 0.133 seconds apart. His opinion
was the product of his calculations regarding the speed at which
the medallion would travel and the distance it would cover given
certain assumptions. In his view, if the white spot were the chain
and medallion, then it would have been in motion, as evidenced
by its presence around the wearer’s neck, rather than near his
navel where it would normally be.
 Dr. Harlow calculated that if the medallion were jerked
upwards as he assumed, then in the 0.133 second space between
frames it would have moved 29 centimetres. On the other hand,
he acknowledged that if the medallion were moving in any
number of other directions, the speed calculations would differ
significantly. Dr. Harlow appears to have been unaware of the
altercation between the shooter and Grant immediately before
the shooting and the possibility that the chain and medallion
could have been in any number of different positions as a result of
The ruling of the trial judge
 The trial judge excluded the proposed evidence. He deter-
mined that the testimony of Dr. Harlow failed to satisfy the
threshold requirements for the admissibility of expert opinion