1. These two appeals involve questions concerning the requirements of the offences of unlawful assembly and riot under sections 18 and 19 respectively of the Public Order Ordinance (Cap 245). 2. The Appellant in FACC 6/2021 (“Lo”) was charged with and convicted of taking part in a riot in Portland Street in Mongkok on 8 and 9 February 2016. 3. Lo’s appeal against conviction was dismissed by the Court of Appeal. On his main ground of appeal, it was held that the defendants’ common purpose of conducting themselves in a disorderly, intimidating, insulting or provocative manner or in a manner endangering the public peace was sufficient to satisfy a requirement of common purpose. 4. The Appellant in FACC 7/2021 (“Tong”) and two others were jointly charged with taking part in a riot with others in the area of Des Voeux Road West near Western Street on 28 July 2019. Tong was acquitted after trial. 5. In the light of his acquittal, the Secretary for Justice referred two questions of law to the Court of Appeal for its opinion pursuant to section 81D of the Criminal Procedure Ordinance (Cap 221). The Court of Appeal held that the common law doctrine of joint enterprise is applicable to the offences of unlawful assembly and riot, so that a defendant may be convicted of those offences even if not present at the scene. 6. On appeal to the Court of Final Appeal, the following issues regarding the offences of unlawful assembly and riot were addressed: (i) whether there is a requirement for proof of a “common purpose” shared by the defendant and other persons taking part in the unlawful assembly or riot; (ii) the applicability of the doctrine of joint enterprise and whether liability can be established without the defendant being present at the scene; (iii) whether a defendant can be found guilty on the basis of mere presence at the scene; and (iv) whether there was any “substantial and grave injustice” arising from the indictment having made no mention of any participants in the riot other than the named co-defendants who were not convicted after trial. 7. The Court examined the inter-related structure of the two offences and noted that both are participatory in nature. The defendant must be shown not just to have been acting alone but to have taken part in the unlawful or riotous assembly together with others so assembled, being aware of their related conduct and with the intention of so taking part. The Court held that there is no requirement for the persons taking part to share some extraneous common purpose. 8. The Court also held that a defendant who is not present at the scene of an unlawful assembly or riot cannot be found guilty as a principal offender because “taking part” in the criminal assembly is a centrally important element of these statutory offences. That requirement cannot be overridden by the common law doctrine of joint enterprise. 9. The Court further held that the basic form of joint enterprise is not applicable to the offences of unlawful assembly and riot even if the defendant was present at the scene, since its application would give rise to duplication and possible confusion regarding the central element of “taking part” in the criminal assembly. 10. However, the Court emphasised that culpable conduct of both present and absent defendants who promote, encourage or act in furtherance of a criminal assembly is covered by secondary and inchoate liability offences and punishable to the same extent as principal offenders. 11. The Court also held that the extended form of joint enterprise may operate to fix participants in the unlawful assembly or riot with liability for more serious offences if they can be proved to have agreed to take part together in the criminal assembly and foreseen commission by one or more of their number of that more serious offence as a possible incident of the execution of their joint plan. 12. The Court held that mere presence at the scene of an unlawful or riotous assembly without more does not give rise to criminal liability. However, a defendant who, being present, provides encouragement by words, signs or actions may be held guilty of “taking part” or as an aider and abettor of the offences of unlawful assembly or riot committed by others. 13. The Court held that that the indictment of Lo was defective but there was no miscarriage of justice given the ample evidence for the jury to be satisfied of Lo’s guilt beyond reasonable doubt. Disposition 14. Accordingly, the Court unanimously dismissed Lo’s appeal.