The High Court has allowed an appeal from the Full Court of the South Australian Supreme Court on admissions and discreditable conduct evidence. Castle and Bucca were convicted by a jury of murdering McDonald, Castle’s former partner, who was shot while sitting in a car driven by Castle. The prosecution’s case was that Castle and Bucca arranged the shooting, with Bucca hiding in the back seat. The defence for Castle contended that the shooter was another person, Gange, who had crept into the car through the car boot, unbeknownst to Castle, and shot McDonald. At trial Pascoe, an associate of Castle and Bucca, gave evidence that Bucca had shown handguns to her father months before the shooting, and that Bucca had said to her father after the shooting that ‘he didn’t mean to do it’. M gave evidence of a conversation between Castle and Bucca on the night of the shooting planning to meet and confront McDonald, and that while Gange had left that night he returned home before before the shooting occurred. Telephone tower records suggest that Bucca and Castle were at the scene of the shooting, and that Gange was not.

The SASCFC held that the trial judge was correct in leaving Pascoe’s evidence on the handguns to the jury as ‘discreditable conduct evidence’, but erred in failing to direct the jury that the statement ‘he didn’t mean to do it’ could not be treated as an admission of guilt by Bucca, on the basis that Pascoe stated Bucca said ‘he’ and not ‘I’, and also erred in failing to direct the jury that the ‘admission’ was not evidence in Castle’s trial. Nonetheless, the SASCFC dismissed the appeal on the basis that these alleged admissions were minor parts of the evidence which were overwhelmed by the prosecution’s circumstantial evidence against the accused and the clear falsity of Castle’s defence: the Court applied the proviso that despite these errors no substantial miscarriage of justice arose in fact.

Before the High Court, Castle contended that the SASCFC erred in concluding that Bucca’s ‘admission’ was unlikely to have affected the verdicts and that her guilt was proved beyond reasonable doubt, that evidence that Bucca possessed handguns some months prior to the shooting were not relevant or admissible as an inference, and that her defence was not fairly left to the jury. Bucca contended that the SASCFC erred in considering whether his guilt had been proved when the admitted error was central to the trial, namely, that the trial judge should have directed the jury that they needed to exclude the reasonable possibility that Bucca referred to a third person as not ‘mean[ing] to do it’ before it could find Bucca guilty, and that in any case the error was a substantial miscarriage of justice.

The Court unanimously allowed both appeals, quashed the convictions, and ordered new trials. The plurality (Kiefel, Bell, Keane and Nettle JJ) held that the SASCFC did not err in holding that Castle’s defence was fairly left to the jury. While the trial judge should not have commented on the reliability of M’s evidence and that she was a ‘fairly decent woman’ (see at [60], [62]), the trial judge did comprehensively and accurately state the submissions of Castle’s defence counsel on the shortcomings of M’s evidence (at [63]). The plurality also held that the SASCFC did not err in holding that the trial judge was correct in allowing the handgun evidence as ‘discreditable conduct’ evidence: the possession of handguns tends to suggest Bucca was engaged in the unlawful possession of firearms, and while the exact make of handgun used in the shooting was not clear, the possession of an item that might have been the murder weapon had considerable probative value (at [77], [78]). But the plurality held that the SASCFC did err in applying the proviso and holding that there had been no substantial miscarriage of justice flowing from the way Pascoe’s evidence on Bucca’s ‘admission’ was left to the jury. Contrary to the SASCFC’s conclusion that the admission was ‘overwhelmed’ by the other evidence which a reasonable jury properly instructed would still have voted to convict, the plurality held (at [65]) that:

what was left to the jury as an admission was, unequivocally, an exculpatory statement. The question was not whether the circumstantial case was so strong as to overwhelm the weight of an admission, but whether the jury might regard the exculpatory assertion as itself a sufficient basis to entertain a doubt as to the strength of the circumstantial case.

While it was open for the SASCFC to see Castle’s oral evidence as ‘glaringly improbable’, proof of guilt did not turn only on the rejection of that evidence, but also on the acceptance of M’s evidence (at [66]ff). Here, despite the strength of the prosecution’s case, the misdirection combined with the limitations of assessing evidence on the record after the trial itself preclude a conclusion that guilt was proved beyond reasonable doubt, and thus required the appeals be allowed and a new trial ordered (at [68]).

Gageler J agreed with the conclusions and reasoning of the plurality, but observed that the ‘admission’ evidence cannot be dismissed as inconsequential and was capable of having significant probative value, and because the real chance that the confession evidence ‘made the difference’ between conviction and acquittal, it is impossible to conclude, as the SASCFC did, that no substantial miscarriage of justice occurred (at [81]).