MLJ Volume 36-1.pdf - Robson Hall Faculty of Law

170 MANITOBA LAW JOURNAL|VOLUME 36 ISSUE 1
IV. THE GENERAL DISCRETION AT COMMON LAW TO
EXCLUDE DEFENCE EVIDENCE WHERE ITS PREJUDICIAL
EFFECT SUBSTANTIALLY OUTWEIGHS ITS PROBATIVE VALUE
The third type of exclusionary discretion concerns defence evidence
and also owes its existence to the common law. In Seaboyer, the Supreme
Court of Canada decided to change the common law, giving life to a new
form of exclusionary discretion: the trial judge can now exclude what is
otherwise technically admissible defence evidence. 131 “[N]o matter how
limited this discretion might or might not be in relation to defence
evidence, the discretion does exist.” 132
Prior to this case, there existed no exclusionary discretion applicable
to defence evidence. 133 If defence evidence was found to be legally
admissible, it would be received regardless of the prejudice it occasioned.
As a result, the general exclusionary discretion existing at common law
first recognized in Wray had no applicability to defence evidence, andthis
continues to be the case under the post-Wray formulation recognized by
the Supreme Court in Seaboyer and Mohan.
However, as a consequence of Seaboyer, a trial judge can now exclude
defence evidence where its prejudice substantially outweighs its probative
value. 134 This standard is more imposing than the formulation applicable
to Crown evidence 135 which requires only that prejudice exceed probative
value, though it is probably not more imposing than the tripartite
standard for exclusion laid down by the Supreme Court in Wray. The
discretion to exclude defence evidence “only becomes engaged where the
prejudicial effect of the evidence substantially exceeds its probative
value.” 136
Unlike the discretion regarding Crown evidence, the discretion
applicable against defence evidence can only be understood with reference
131
Seaboyer, supra note 56 at 611.
132
R v TJB, 2004 CarswellNfld 122 at para 6 (WL Can), 2004 CanLII 16157 (PC) [TJB].
133
See generally, Paciocco & Stuesser, supra note 1 at 38.
134
Seaboyer, supra note 56 at 611; aff’d R v Shearing, 2002 SCC 58 at para 107, [2002] 3
SCR 33.
135
See Paciocco & Stuesser, supra note 1 at 38-39 for a discussion of the rationale behind
the more imposing standard applicable to defence evidence.
136
R v Palma (2000), 149 CCC (3d) 169 at 175 (available on WL Can) (Ont SCJ).