This study represents an attempt to delineate one major aspect of these societal attitudes. Its thesis is that from late Anglo-Saxon times to the end of the middle ages, there existed a widespread societal distinction between ‘murder,’ i.e., homicide perpetrated through stealth, and simple homicide, roughly what a later legal age termed manslaughter. This distinction, which was imposed upon the courts through the instrument of the trial jury, was fundamentally at odds with the letter of the law. It is therefore necessary to state, if only briefly, what the rules of law were.
In the early twelfth century, the Crown took exclusive jurisdiction over all homicides and defined them as 1) culpable and thereby capital, 2) excusable and thereby pardonable, 3) justifiable and thereby deserving of acquittal. The last class at first incorporated the slaying of handhaving thieves and outlaws who resisted capture. By the middle of the fourteenth century, it came to include the killing of housebreakers and robbers caught in the act, though it was not until the sixteenth century that a statute made this policy into firm law. Pardonable homicides were those committed by the insane, unintentional homicides and homicides committed in self-defence. The rules of self-defence were rigorous throughout the entire mediaeval period. The slayer had to have made every possible attempt to escape his attacker, must have reached a point beyond which he could not retreat and must have retaliated out of literally vital necessity. All other homicides, those deliberate but of a sudden as well as those planned and stealthily perpetrated fell into the large category of culpable homicide; according to the rules of the law, there were to be no distinctions made among them. This remained true until the late sixteenth century when the judicial distinction between murder and manslaughter finally emerged.
Thomas A. Green, “Societal Concepts of Criminal Liability for Homicide in Mediaeval England” (1972)