R v Powell and English  3 WLR 959;
 1 AC 1;  4 All ER 545;  1 Cr App R 261; (1998) 162 JP 1;  Crim LR 48
MURDER, MENS REA, JOINT ENTERPRISE, FORESEEABILITY, SECONDARY CRIMINAL LIABILITY
In the first case, the appellants Powell (P) and Daniels (D), and another person went to the house of a drug dealer. As soon as he opened the door, he was shot dead by one of the three people. At the trial P provided evidence that he only went to the dealer’s house to buy cannabis. D did not give any evidence, but argued that P was responsible for the shooting and that he was not aware of the presence of the gun until it was fired. P and D were convicted of murder on the basis of joint enterprise. The Court of Appeal dismissed their appeal and they appealed to the House of Lords.
In the second case, the appellant English (E) and another person (W) attacked a police officer with wooden posts. During the attack, W stabbed the police officer with a knife, which caused his death. Both E and W were convicted of murder on the basis of joint enterprise. E appealed his conviction and the Court of Appeal dismissed it as a result of which he turned to the House of Lords.
What level of mens rea is required in order to convict a secondary party to a joint enterprise of murder?
(1) Where there is joint enterprise to commit a crime, to found a conviction of murder for a secondary party, it is enough to show that they contemplated that the primary party might kill with intent to do so or cause serious injury. Thus, P and D’s appeal was dismissed.
(2) If a secondary party did not foresee that the principal might commit an act which was fundamentally different from the one jointly contemplated, they could not be guilty of murder unless the weapon that caused the death of the victim was just as dangerous as the one contemplated. Hence, E’s appeal was allowed.
With this ruling, the House of Lords overruled R v Barr  88 Cr. App. R. 362.