Development of Defense of Provocation Question: Critically evaluate the development of common law principles applicable to the defence of provocation in criminal law from the decision in Mancini v DPP [1942] AC 1 to Mascantonio v R (1995) 183 CLR 58. Assess the degree to which the common law has proved inflexible in responding changing societal needs and expectations. Are there other legal means of achieving substantive justice? At the time of the case of Mancini the concept of provocation as a defence to murder was already a well established one dating back centuries. It originated from the days when men bore arms and eng