“Put shortly, the case was left to the jury on the basis that the gunman was guilty of murder and that others who joined him for the common purpose of killing or causing Wilson serious harm by means of the gun would be guilty of murder also. Gaffney, Lindsay and Green all contended that the use of the gun was outside the common design which was to tell Wilson to stay away from Leeds and McKenny (Gaffney) and “rough him up” (Lindsay and Green). McKenny’s case was that she had no idea that serious violence would be used.”