R v Jogee  UKSC 8
Parasitic Accessory Liability, intention and foresight of principal’s act
This joint case involved two separate appellants who had been convicted for murder on the basis of joint enterprise, after a co-defendant had actually killed the victim. In the case of Jogee, he had been vocally encouraging the principal while he murdered a police officer. In the case of Ruddock, liability was based on his participation in a botched robbery during which the principal murdered the victim (an act which the principal admitted). In Jogee, the judge made the direction that liability as an accessory would attach where the defendant participated in the attack while realising that the principal might stab the victim while intending to cause really serious harm. In the case of Ruddock, the judge made the direction that it was necessary to establish a shared common intention between the principal and the accessory and this could be proved where the defendant was shown to have known that there was a real possibility that the principal might intend to commit a given crime (in that case GBH or murder) and still continued with his participation in the joint enterprise.
The court had to determine whether the principle of Parasitic Accessory Liability, as established in Chan Wing-Siu v The Queen  1 AC 168, is a correct exposition of the law.
The court held that in order to prove accessorial liability, it was not sufficient to only prove the necessary mental element, but also the element of conduct. This could be discharged by proving that the accessory either assisted or at least encouraged the principal in committing the offence. The mental element is discharged by proving that the accessory intended to so assist or encourage the principal. The mental element however is not discharged by mere foresight that the principal might commit an offence. Chan Wing-Siu v The Queen  1 AC 168 was incorrectly decided in the part of equating foresight with intent. The convictions were therefore quashed and R v Collinson (1831) 4 Car & P 556, R v Smith (Wesley)  1 WLR 1200, CCA and R v Reid (Barry) (1976) 62 Cr App R 109, CA were approved.