In criminal law, the venerated rule of lenity has been frequently, if not consistently, invoked as a canon of interpretation. Where criminal statutes are ambiguous, the rule of lenity generally posits that courts should interpret them narrowly, in favor of the defendant. But the rule is not always reliably used, and questions remain about its application. In this article, I will try to determine how the rule of lenity should apply and whether it should be given the status of a canon.
First, I argue that federal courts should apply the historical rule of lenity (also known as the rule of strict construction of penal statutes) that applied prior to the 1970s, when the Supreme Court significantly weakened the rule. The historical rule requires a judge to consult the text, linguistic canons, and the structure of the statute and then, if reasonable doubts remain, interpret the statute in the defendant’s favor. Conceived this way, the historical rule cuts off statutory purpose and legislative history from the analysis, and places a thumb on the scale in favor of interpreting statutory ambiguities narrowly in relation to the severity of the punishment that a statute imposes. As compared to the modern version of the rule of lenity, the historical rule of strict construction better advances democratic accountability, protects individual liberty, furthers the due process principle of fair warning, and aligns with the modified version of textualism practiced by much of the federal judiciary today.
Second, I argue that the historical rule of lenity should be deemed an interpretive canon and given stare decisis effect by all federal courts. If courts consistently applied historical lenity, it would require more clarity from Congress and less guessing from courts, and it would ameliorate some of the worst excesses of the federal criminal justice system, such as overcriminalization and overincarceration.