Perry v The Queen

This matter concerns an application for special leave to appeal to the High Court of Australia by Roderick Hilton Perry. The applicant was convicted of the murder of John Greentree. The Crown was represented by Mr R.N. Howie, QC, and Mr P.G. Berman, while the applicant was represented by Mr J. Basten. The dispute centres on the admissibility of psychiatric evidence concerning the applicant's mental state at the time of the killing.

The primary legal issue before the High Court was whether psychiatric opinion evidence, which concluded that the applicant suffered from paranoid delusions and an abnormality of mind, was admissible when the factual basis for those delusions (specifically, a belief of sexual assault) could not be independently corroborated. The Court was required to consider whether such evidence could be tendered to establish diminished responsibility when the truth or falsity of the underlying belief was not demonstrably disproven.

The High Court considered the judgment of the Chief Justice in the Court of Criminal Appeal, which held that psychiatric opinion evidence could not be used to conclude that a belief was a paranoid delusion if the belief itself was not self-evidently irrational or mistaken, and if there was no independent evidence to disprove it. The Chief Justice reasoned that it was not open for a party to tender psychiatric opinion to assert that a belief was a delusion, and then further conclude that the belief was not a result of mistake or dishonesty but of a paranoid delusion, without establishing the factual basis for the belief. The Court acknowledged the general principle that opinion evidence requires an established factual basis to be of worth.