"The prosecution case is that the defendants committed this murder jointly. Where the offence is committed by two or more persons, each of them play a different part, but if they’re acting together as part of a joint plan to commit an offence, they are each guilty of it. Before you can convict any of the defendants you must either be sure that he committed the murder himself or that he did an act or acts as part of a joint plan with the other defendants to commit murder. If you are not sure that he was killed by the defendant whose case you are considering you must go on to decide whether the defendant whose case you are considering was a party to a joint enterprise which included either an agreement, tacit or express, involving the intention to kill Clarence Cooper or to cause him really serious bodily harm if the need arose during the course of the burglary; or, without agreeing to such conduct being used, the realisation that Clarence Cooper might be killed or caused really serious bodily harm during the burglary. ... What about B and C who are party to the joint enterprise to burgle the house? The law is that where two or more persons embark on a joint criminal enterprise, in this case burglary, each is liable for the acts done in pursuance of that joint enterprise, and that includes liability for the unusual consequences if they arise from the carrying out of the joint enterprise. However, if one of the burglars goes beyond what had been agreed between them as part of the joint enterprise and does an act which is outside the scope of what has been agreed between them, then the others are not liable for the consequences of that unauthorised act. It is for you to decide whether what was done was part of the joint enterprise or went beyond it and was in fact an act unauthorised by the joint enterprise. ... In any of those situations it is open to you to conclude that the defendant whose case you are considering was a secondary party to the joint enterprise, but you must also be sure that the joint enterprise in which he participated included either an agreement involving an intention to kill Clarence Cooper, or to cause him really serious harm if the need arose during the burglary, or without agreeing to such conduct being used the realisation that Clarence Cooper might be killed or might be caused really serious bodily harm in the course of the burglary. In fact, the way the prosecution put their case is that the secondary parties to the joint enterprise must have realised or contemplated that really serious harm might be intentionally inflicted on Clarence Cooper, and that they nevertheless continued to participate in the burglary. If, therefore, you are sure that one of the three defendants killed Clarence Cooper with the requisite intention for murder, namely to kill or to cause really serious bodily harm, and that the killing occurred during the execution of a joint enterprise which involved the realisation that serious bodily harm might be intentionally inflicted on Clarence Cooper, and if you are sure that the defendant whose case you are considering participated in that joint enterprise with that realisation, then the defendant whose case you are considering will be guilty of murder."
"Thirdly, are you sure that one of the defendants, other than the defendant whose case you are considering, killed Clarence Cooper with the intention to kill him or to cause him really serious bodily harm? If yes, consider question 5; if no, consider question four. Fourthly, are you sure that one of the defendants, other than the defendant whose case you are considering, killed Clarence Cooper in circumstances that all reasonable and sober people would inevitable realise must subject someone to the risk of some harm although not serious harm? If yes, consider question 7; if no, find him not guilty of murder and manslaughter. Fifthly, are you sure that the defendant whose case you are considering took part in a joint enterprise with the defendant who killed Clarence Cooper to burgle 178 Alexandra Road? If no, find him not guilty of murder and manslaughter. If yes, consider question 6. Sixthly, are you sure that the joint enterprise in which the defendant whose case you are considering took part included the realisation by him that really serious bodily harm might be intentionally inflicted on Clarence Cooper? If yes, find him guilty of murder; if no, consider question 7. Seventhly, are you sure that the joint enterprise in which the defendant whose case you are considering took part involved a realisation by him that some harm might be caused to Clarence Cooper? If yes, find him guilty of manslaughter; if no, find him not guilty of murder and manslaughter. You probably realise by now, members of the jury, why I thought it might be helpful if you were to have those directions in writing so that you can take them out with you and consider them when you retire."
"Mr Sallon, for the appellant, advanced to your Lordships' House the submission (which does not appear to have been advanced in the Court of Appeal) that in a case such as the present one where the primary party kills with a deadly weapon, which the secondary party did not know that he had and therefore did not foresee his use of it, the secondary party should not be guilty of murder. He submitted that to be guilty under the principle stated in Chan Wing-Siu the secondary party must foresee an act of the type which the principle party committed, and that in the present case the use of a knife was fundamentally different to the use of a wooden post. My Lords, I consider that this submission is correct. It finds strong support in the passage of the judgment of Lord Parker C.J. in Reg. v. Anderson; Reg. v. Morris [1966] 2 Q.B. 110, 120 which I have set out earlier, but which it is convenient to set out again in this portion of the judgment: 'It seems to this court that to say that adventurers are guilty of manslaughter when one of them has departed completely form the concerted action of the common design and has suddenly formed an intent to kill and has used a weapon and acted in a way which no party to that common design could suspect is something which would revolt the conscience of people today.'. The judgment in Chan Wing-Siu's case [1985] A.C. 168 also supports the argument advanced on behalf of the appellant because Sir Robin Cooke stated at p.175: 'The case must depend rather on the wider principle whereby a secondary party is criminally liable for acts by the primary offender of a type which the former foresees but does not necessarily intend.’ (Emphasis added.)"
"However, I would wish to make this observation: if the weapon used by the primary party is different to, but as dangerous as, the weapon which the secondary party contemplated he might use, the secondary party should not escape liability for murder because of the difference in the weapon, for example, if he foresaw that the primary party might use a gun to kill and the latter used a knife to kill, or vice versa."
"If you are sure that the defendant realised that a screwdriver or knife might be used with the intention of causing (at least) serious bodily harm to Clarence Cooper and if you are sure that the defendant realised that one of the burglars may, with the intention that serious bodily harm be caused to Clarence Cooper (by himself or another), take steps to silence the victim’s voice, then he is guilty of murder [the other ingredients being satisfied]."