In the upper-left quadrant of Grant’s jacket, a forensic
biologist located five areas of staining, including two encrusted
areas. Four of these five areas, including one that was encrusted,
contained a DNA profile in which Peter Johnson was the major
contributor. The probability of another person being the source of
this DNA was one in 5.7 billion.
 Albert Grant had frisk-searched Peter Johnson earlier in
the evening before the shooting occurred.
The Grounds of Appeal
 Peter Johnson (the “appellant”) challenges two decisions
made by the trial judge. He says that the trial judge was wrong:
( i) in ruling inadmissible the proposed expert opinion evidence
of Dr. Jason Harlow about the likelihood that a white spot
apparent on a surveillance video was a chain and medallion
around the neck of the shooter; and
( ii) in failing to instruct the jury on the statutory partial defence
of provocation on the count charging the appellant with sec-
ond degree murder.
Ground #1: The Expert Opinion Evidence
 The critical issue at trial was the identity of the shooter,
the man whom Albert Grant subdued in a headlock then released
when the man ceased to struggle with Grant. None of the eyewit-
nesses to the incident identified the appellant or anyone else as
 To establish that the appellant was the shooter, the Crown
relied upon the evidence of Det. Idsinga who, over hundreds of
hours, reviewed the surveillance video from inside and outside
Whispers and compared a list of identifiers consisting of items of
clothing and bodily appearance that matched only the appellant.
The identifiers included a long chain and a medallion around
the neck of the shooter. On arrest, police seized a long chain and
medallion from the appellant who admittedly was at Whispers
 Some additional background is helpful for an understanding of the evidence tendered for admission and the trial judge’s
reasons for excluding it.
The white object
 At times on the surveillance video and screenshots taken
from it, a white object is visible around the shooter’s neck. The
Crown contended that the object was a medallion attached to