McMahon v The Queen

McMahon appealed his conviction for murder in the Supreme Court of New South Wales. The appeal concerned the admissibility of certain evidence and the directions given to the jury.

The High Court of Australia was required to determine whether the trial judge erred in admitting evidence of the appellant's prior convictions and whether the judge's directions to the jury regarding the use of that evidence were adequate. Specifically, the court considered whether the prejudicial effect of the evidence of prior convictions outweighed its probative value, and whether the jury was properly instructed on the limited purpose for which such evidence could be considered.

The High Court held that the admission of the evidence of prior convictions was an error. Their Honours found that the evidence was not sufficiently relevant to the issues in the trial and that its prejudicial effect was substantial. The jury directions were also found to be inadequate, failing to sufficiently mitigate the prejudice arising from the admission of the prior convictions. Consequently, the High Court allowed the appeal, quashed the conviction, and ordered a new trial.