Mansfield v The Queen & Anor; Kizon v The Queen & Anor

The High Court of Australia considered appeals from the Court of Appeal of Western Australia in two related matters, *Mansfield v The Queen* and *Kizon v The Queen*. The appeals concerned the admissibility of evidence obtained through covert surveillance and the proper application of the *Criminal Investigation Act 2006* (WA) in relation to the use of listening devices. The central dispute revolved around whether the evidence gathered by police, purportedly under the authority of a warrant, was lawfully obtained and therefore admissible in the criminal proceedings against the appellants.

The primary legal issues before the High Court were whether the warrants issued for the use of listening devices were validly granted, and consequently, whether the evidence obtained through their use was admissible. Specifically, the Court had to determine if the police had complied with the requirements of the *Criminal Investigation Act 2006* (WA) when seeking and executing the warrants, particularly concerning the necessity of the surveillance and the information provided to the issuing officer. The Court also considered the implications of any non-compliance for the admissibility of the evidence under the Act.

The High Court reasoned that the validity of the warrants was contingent upon strict adherence to the statutory requirements. It was held that the issuing officer must be satisfied that the use of a listening device is an appropriate, proportionate, and necessary means of obtaining evidence. The Court found that in this instance, the information presented to the issuing officer was insufficient to establish necessity, and therefore the warrants were invalidly issued. Consequently, the evidence obtained through the use of the listening devices was unlawfully obtained and inadmissible under section 139 of the *Criminal Investigation Act 2006* (WA), which mandates the exclusion of evidence obtained in contravention of the Act.

The appeals were allowed, the convictions were quashed, and the matters were remitted to the Court of Appeal of Western Australia for further consideration.