Common Design in UK Law

The underlying concept for joint tortfeasance must be that the joint tortfeasor has been so involved in the commission of the tort as to make himself liable for the tort. Unless he has made the infringing act his own, he has not himself committed the tort. If there is a common design or concerted action or otherwise a combination to secure the doing of the infringing acts, then each of the combiners has made the act his own and will be liable.

It seems to this Court that to say that adventurers are guilty of manslaughter when one of them has departed completely from 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.

There was clearly a common design to rob, but that would not suffice to convict of murder unless the common design included the use of whatever force was necessary to achieve the robbers' object, (or to permit escape without fear of subsequent identification), even if this involved killing, or the infliction of grievous bodily harm on the victim.