Section 21(2) enlarges the scope of who is a party to an offence beyond those who knowingly aid or abet an offence by providing that those who "form an intention in common to carry out an unlawful purpose and to assist each other therein" are parties to any consequential of-fence committed by one of them provided that the accused "knew or ought to have known that the commission of the offence would be a probable consequence of carrying out the common purpose." Thus, a person who forms a common unlawful intent (for example, to engage in a robbery) is a party to other offences that he or she knew or ought to know would probably occur (such as forcible confinement or manslaughter). In practice, section 21(2) applies when the principal has committed crimes beyond which the parties have intended to aid and abet.129
Under section 21(2) there must be a formation of a common intent to assist each other in carrying out an unlawful purpose, but not necessarily any act of assistance.130It could be argued that this requires an agreement akin to conspiracy, although most cases do not dwell on the issue. In addition, it is assumed that the unlawful purpose means a purpose contrary to the Criminal Code. The subsequent offence committed has to be one that the accused either knows or ought to have known would be a probable consequence of carrying out the common purpose. In Jackson,131the Supreme Court held that the offence is not confined to that which the principal was convicted, but encompasses any included offence. For example, a party to an unlawful purpose could be convicted of manslaughter, even though the principal was convicted of murder. This would happen when the party did not have the subjective foresight of death required for a murder conviction, but did have objective foresight of bodily harm necessary for a manslaughter conviction. Less clear is whether a party with the mens rea for murder can be convicted of murder even though the principal offender was only convicted of manslaughter. There is some authority that the party
could only be convicted of the same offence as the principal offender,132 but general principles as well as section 23.1 suggest that a party with the required mens rea could be convicted of a more serious offence than a principal offender. For example, a sober or unprovoked accomplice might have the mens rea for murder even though the actual drunken or provoked killer might only have the mens rea for manslaughter.133
There are two distinct mental or fault elements for section 21(2): the first is the formation of the common unlawful purpose and the second is either subjective knowledge or objective foresight that the actual of-fence would be a probable consequence of carrying out the unlawful purpose.
In R. v. Paquette,134the Supreme Court held that a person who drove others to a robbery had not formed a common unlawful purpose to assist them in the robbery because he had been forced at...