Murphy (a pseudonym) v The King

The appeal concerned Murphy (a pseudonym) and The King. The dispute revolved around the evidentiary basis for a finding of mental incompetence at trial, specifically in relation to the appellant's diagnosis of Autism Spectrum Disorder (ASD). The matter was heard by Livesey P, Lovell J, and Buss AJ.

The central legal issue before the court was whether the trial had miscarried due to an irreconcilable dispute between the parties regarding the proof of the factual basis for expert opinions on the appellant's mental incompetence. This dispute concerned whether the prosecution had conceded that ASD constituted a "mental illness" and "mental impairment" for the purposes of the relevant legislation, and whether the appellant had adequately proven the facts underlying the expert diagnoses.

The Court found that the parties were not ad idem concerning their approach to the evidence at trial, a misunderstanding that only became apparent on appeal. The prosecution contended that the appellant failed to prove the facts underlying the expert opinions, while the appellant argued the prosecution had conceded the diagnostic aspects and only disputed the application of the legal test. The Court determined that this fundamental disagreement about the evidentiary material could not be resolved by reference to onus of proof or by reading the transcript and submissions. Consequently, the Court concluded that the hearing had miscarried because the disagreement could not be fairly resolved, and it was not open for the appellate court to form its own view of the evidence.

Given that the mental competence investigation had miscarried, the Court ordered a new trial.