Mens Rea by the Numbers

Before the recent presidential election, a bipartisan congressional effort was made to pass a criminal justice reform bill. The bill faltered in part because of a proposed default mens rea provision: statutes silent on mens rea, that were not explicitly identified as strict liability by the legislature, would be taken to require for guilt proof of knowledge with respect to each material element. This paper focusses on a prominent line of disagreement about the default mens rea provision. Proponents argued that it would reduce the number of unjust verdicts in corporate cases. They noted that there have been convictions of corporations and corporate officers for public welfare offenses in instances in which there was good reason to believe that the defendants lacked mens rea. They touted the legislation, then, as a way of reducing the false positive rate. Opponents noted that the provision would also reduce the rate of true positives in corporate prosecutions—convictions of those possessing mens rea who could not be proven to—and opposed the legislation on those grounds. Both sides, then, accepted that the relevant question was, in part, numerical: under the provision, would the reductions in guilty verdicts of those lacking mens rea outnumber and outweigh the increases in acquittals of those possessing it? This paper critically examines this numerical approach for assessing and justifying the default mens rea provision. The paper argues that there is a small domain under which it is appropriate to reason in such numerical terms about a default mens rea provision, but that that domain is so small as to make such arguments inappropriate when it comes to sweeping legislation, such as that proposed. The paper further argues that in light of this conclusion the default mens rea provision must be examined non-numerically, through appeal to principled considerations about the necessary conditions for morally justified infliction of punishment. When such arguments are freed from numerical considerations of the kind that dominated the public discussion of the legislation, they decide the matter: the default mens rea provision deserves bipartisan support.