Two Sides of the Same Interpretive Coin: The Presumption of Mens Rea and the Historical Rule of Lenity

Shon Hopwood

Distinguished Professor of Philosophy 
Associate Professor of Law Georgetown University Law Center

In the past forty years, Congress has passed thousands of federal criminal laws, many of which are unclear on their face. Sometimes Congress omits important information and fails to define key terms. Other times it drafts criminal statutes so imprecisely that courts have found them unconstitutionally vague.5 And because its members often imagine the worst offenders when drafting criminal laws, Congress frequently writes laws so broadly as to include innocent conduct unrelated to the harms it intends to criminalize. As Professor Dan Kahan has noted, “criminal statutes typically emerge from the legislature only half-formed.”