The prior conviction was admissible as “some evidence” linking the appellant to the assault on J.S. In the context of a similar fact application, a prior conviction may be tendered to establish an essential element of the prior offence where that element has been placed in issue. The admissibility of a prior conviction does not depend on whether it was the product of a guilty plea or a post‑trial guilty verdict. Verdicts should not be viewed as hearsay or opinion evidence of questionable value. Whether rendered by a jury or by judge alone, they are presumptively reliable and, on the issue of identity, should be treated that way unless overturned on appeal or later shown to be wrong.
Because similar fact evidence is presumptively inadmissible, its probative value must exceed its prejudicial effect.
First, it is not uncommon for a trier of fact to be exposed to a prior conviction, in the form of a guilty plea, which stems from the similar fact evidence the Crown seeks to lead. The trier of fact is made aware of the limited use that can be made of the similar fact evidence, and the accused can challenge or explain the prior conviction.
Second, while a prior conviction constitutes strong proof that the similar act conduct in question occurred, that does not make the conviction inadmissible. The fact that a piece of evidence operates unfortunately for an accused does not render the evidence inadmissible or the trial unfair.
Third, an accused is entitled to a fair trial, not a trial in which the playing field is tilted in his or her favour. Once an accused challenges his or her involvement in an earlier incident, the rules of evidence do not permit the accused to keep the best evidence linking him or her to that incident — the conviction — from the trier of fact.
While an accused should not be automatically foreclosed from challenging a prior conviction at the voir dire stage of a similar fact application, situations in which such a challenge may be launched will be rare because of the low evidentiary threshold (“some evidence”) required to link an accused to the similar act. A challenge at the voir dire stage will not be appropriate if there is no reasonable likelihood that it will impact the admissibility of the evidence. In deciding whether the conviction can be challenged, labels such as res judicata and abuse of process are unhelpful and inappropriate — neither of these doctrines can prevent an accused from challenging a prior conviction on a voir dire. The decision to allow a challenge or not at the voir dire stage is a function of the trial judge’s right to control the proceedings.
Source: R. v. Jesse, 2012 SCC 21