Director of Public Prosecutions (NSW) v JS

The Director of Public Prosecutions (NSW) sought to appeal a decision of the Local Court to the Supreme Court, challenging the acquittal of a defendant in the Children's Court on a charge of unauthorised possession of a pistol. The appeal focused on a question of law concerning the admissibility of an expert certificate from a forensic ballistics expert that was crucial to the prosecution's case. The Local Court excluded the certificate, finding that there was insufficient "line" between the expertise of the certificate's maker and the identification of the pistol in question. The Supreme Court was tasked with determining whether this exclusion constituted an error of law warranting an appeal.

The central legal issue before the Supreme Court was whether the exclusion of the expert certificate was a question of law or fact, and if so, whether the Local Court Magistrate erred in law by excluding the certificate. The court needed to interpret section 177(1)(c) of the Evidence Act, which pertains to the admissibility of evidence based on specialised knowledge, and determine the meaning of the phrase "expressed to be wholly or substantially based on that knowledge." The prosecution argued that the exclusion was an error of law, as the expert's knowledge was sufficient to form the basis of the certificate.

The Supreme Court held that the exclusion of the expert certificate was indeed a question of law. It found that the Local Court Magistrate had misapplied the test under section 177(1)(c) of the Evidence Act by incorrectly assessing the "line" between the expert's knowledge and the identification of the pistol. The court clarified that the test requires an assessment of whether the evidence is based on specialised knowledge, not a comparison of expertise. Consequently, the Supreme Court quashed the acquittal and remitted the matter back to the Local Court for a new trial. The court emphasised the importance of correctly applying the legal principles governing the admissibility of expert evidence.