In a long-awaited and unusual joint judgment of two peak courts, the UK Supreme Court and the Privy Council, five judges yesterday ruled that the common law took a ‘wrong turn’ on the criminal law of complicity at least 19 years ago.The courts heard appeals by people convicted of murder after their partners in crimes –  respectively, an English domestic assault and a Jamaican taxi robbery –  instead stabbed the intended victims. At issue were rulings by the Privy Council in 1985 and the House of Lords in 1997, building on decisions by Australia’s High Court from 1980,  that such defendants could be convicted of murder if they were merely aware that their accomplices ‘might’ murder someone in the course of another crime. Yesterday’s unanimous judgment found that the twin decisions misunderstood the earlier authority, disregarded principle and, most disturbingly, ‘bring the striking anomaly of requiring a lower mental threshold for guilt in the case of the accessory’ – the accomplices’ awareness of the possibility of a murder -‘ than in the case of the principal’- the stabbers’ intent to cause serious harm. Accordingly, they overruled the 1985 and 1997 decisions, detailed a new narrower standard for liability and outlined ground rules for reviewing decades of potentially wrong convictions.

But yesterday’s ruling does not apply in Australia. Rather, its reach is confined to common law jurisdictions governed by the UK Supreme Court (England and Wales) or the Privy Council (including Jamaica.) The Privy Council ceased to hear Australian appeals in 1986 and, anyway, Australia’s High Court had long held that all overseas judgments are merely persuasive about the content of the ‘common law of Australia’. For Australians, yesterday’s ruling is merely another example, albeit an especially dramatic one, of how other nations’ common law has diverged from Australia’s. The divergence is partly at the level of criminal law theory, with the UK Supreme Court ‘ respectfully differ[ing] from the view of the Australian High Court, supported though it is by some distinguished academic opinion’ that the cases at issue represent ‘a separate form of secondary liability’ from other sorts of complicity. But the divergence is also on how the two courts develop the common law. In 2006, the High Court rejected a similar opportunity to declare that Australia’s law of complicity had taken a wrong turn, stating that any change  ‘is a task for legislatures and law reform commissions’. Yesterday, the UK Supreme Court firmly rejected that approach: ‘the doctrine of secondary liability is a common law doctrine… and, if it has been unduly widened by the courts, it is proper for the courts to correct the error’.

None of this means that yesterday’s ruling is irrelevant in Australia. Although it is not bound by UK decisions, the High Court typically pays them close attention. Indeed, the High Court relied on the 1985 Privy Council decision in 1995 to reach the same conclusion on the law of complicity that the House of Lords adopted in 1999. And one of the Court’s reasons for not changing the law of complicity in 2006 was that ‘[o]ther common law countries continue to apply generally similar principles’, with a footnote referencing both now-overruled UK decisions. As it happens, the High Court will soon hear three joint Australian appeals involving the same contentious doctrine. In addition, yesterday’s dramatic ruling will surely provide a further basis for Australia’s legislatures to reform the common law. Victoria’s Parliament did so in 2014, abolishing the common law and replacing it with a statutory formulation along the lines of the alternative doctrine rejected by the High Court in 2006.