From Principles to Rules
An Introduction to Mens Rea
Now we move from principles of deserved punishment to rules of law, from generalities about blameworthiness to defining and grading different categories of homicidal conduct. In a sense we move to more familiar territory, for the basic considerations involved in defining homicide offenses are the same as we use in everyday human interaction—considerations of intent, awareness and motive, calculation and accident, passion and dispassion. But here we also enter the realm of lawyers and the particular traditions of Anglo-American criminal law.We enter a linguistic thicket, in which special historical and legal meanings about terms like malice, premeditation and provocation, must be considered. Almost as troublesome, though, will be the ordinary language of blameworthiness, which for all its suggestive power contains many traps for the conceptually unwary.
My task in this chapter is threefold: (1) to introduce the concept of mens rea as it applies to murder and manslaughter; (2) to introduce some of the competing criteria for mens rea rules; and (3) to defend basic mens rea analysis against two fundamental objections, one arising out of new work in cognitive science, and another that comes from a common misconception about how we understand and judge each other's choices.
As a preliminary matter, we need to canvass the variety of different rules that come under the heading of mens rea—all the different principles involving intent to harm and awareness of harm, culpable risk taking, motive, and quality of decision making that form the core of the law of murder and manslaughter. Once these basics are in hand we turn briefly to considerations of rule drafting. Not only must we decide what kinds of culpable conduct an offense should cover, but we also must decide how to express our judgment in mens rea rules.This proves to be a matter of both substance and style.The broadest and most nuanced rules tend to be those in which aspects of mens rea are defined by allusion to character traits. But these same allusive forms of mens rea suffer most from the ills of vagueness, threatening to violate the