The appellant, Adrian Daou, appealed his conviction for first-degree murder.
The Crown's case relied heavily on confessions made by the appellant to police while he was incarcerated and suffering from schizophrenia.
The lead investigator, Det. Monette, testified that he believed the confession was true, providing detailed reasons.
The Court of Appeal found this police opinion evidence inadmissible as it amounted to an opinion on the appellant's guilt and usurped the jury's function.
The trial judge erred by failing to provide a limiting instruction and by reiterating the officer's opinion.
The court declined to apply the curative proviso, finding that the inadmissible evidence and lack of caution seriously risked dominating the jury's consideration of the confession's veracity and the appellant's guilt, thus resulting in an unfair trial.
The appeal was allowed, the conviction set aside, and a new trial ordered.