The Judicial Committee of the Privy Council wrongly interpreted the common law when they developed the principle of “parasitic accessory liability”. Foresight should not be equated with intent. Foresight is simply evidence (albeit sometimes strong evidence) of intent to assist or encourage the principle to commit the crime, with the required mens rea for that crime, which is the proper mental element for establishing secondary liability.
The appellants were each convicted of murder as secondary parties following directions to the jury applying the principle of "parasitic accessory liability" developed in Chan Wing-Siu  AC 168 and R v Powell and English  1 AC 1.
Appeals against conviction were heard in the Supreme Court (Jogee) and by the Judicial Committee of the Privy Council (Ruddock). The Supreme Court undertook a thorough review of the authorities concerning accessory liability and parasitic accessory liability.
1 The law took a wrong turn in the case of Chan Wing-Siu  AC 168 the Privy Council created a new principle based on an incomplete, and in some respects erroneous, reading of the common law, coupled with questionable policy arguments.
2 This mistake had created a lower culpability threshold for secondary parties in a joint enterprise than existed for primary ones.
3 The Supreme Court found that a secondary party's foresight should be regarded only as evidence (albeit sometimes strong evidence) of intent. Foresight should not be automatically equated with authorisation or an intention to engage in the primary party's crime.
4 This brings the law back into line with the well-established rule prior to Chan Wing-Siu that the mental element required of a secondary party is an intention to assist or encourage the principal to commit the crime. If the crime requires a particular intent then the secondary party must intend to assist the primary party to act with that intent.
5 It will remain relevant to enquire in most cases whether the principal and secondary party shared a common criminal purpose, and the nature of this purpose, often this will demonstrate the extent of the secondary party's intention to assist.
6 The impact of this judgment is not to render invalid all convictions reached through the incorrect application of the law. The important issue will be if the principle, as applied to the facts, was material to the outcome of the trial or the safety of the conviction. Prospective appellants will have to seek exceptional leave to apply to the Court of Appeal out of time, and that leave will only be granted if substantial prejudice can be demonstrated. This will not be found simply on the basis that the law has changed. The same may also be said of applications to the Criminal Cases Review Commission.
Appeals partially allowed: Convictions for murder to be set aside.
21 March 2016