It used to be that all crimes required two basic elements: an actus reus (a prohibited act) and a mens rea (a guilty mind). In recent years, however, there have been a growing number of strict liability crimes that dispense with the mens rea element in state criminal codes.

This summer, the Federalist Society released a survey of state mens rea requirements by Professor John S. Baker, Jr. It begins by tracing the history of mens rea requirements and the rise of strict liability offenses. The history highlights the Model Penal Code’s (MPC) introduction of a default mens rea provision.

The MPC requires that for all crimes without an explicit culpable mental state, and without language clearly dispensing of one, the default mental requirement shall be “purposely, knowingly, or recklessly.” This provision was intended to guarantee that a culpable mental state remained a necessary element for any crime. The study concludes, however, that the MPC’s default mens rea provision has actually had the effect of weakening the role of the mental state in state criminal law.

The study offers three reasons for this paradox. First, the MPC has “‘purposely’ stripped culpability of its normative quality.” Second, “[c]odification freed state legislatures from a sense of obligation to common-law principles.” Third, states that have not followed the MPC’s strict distinction between crime and violation have problematically “opened up possibilities of interpretation by the courts.”

The survey focuses on the fourteen states that have adopted the MPC mens rea provision or a similar provision, and it points out some of the common problems the states’ courts have faced when interpreting the requirement.

Among these problems are the courts’ struggles to interpret legislative intent and a disparity in how much analysis appellate courts do when determining legislative intent. It highlights concerns that courts have about defendants’ constitutional challenges for vagueness or due process violations, concerns about non-blameworthy conduct being criminalized, and the provision’s applicability outside of the criminal code.

Finally, the study encourages states to reassess the adequacy of the MPC’s default mens rea framework. It suggests that the “erosion of mens rea since the advent of the MPC” requires that particular rules need to “reflect the primacy of the principle of mens rea in criminal law.”