This article answers two key questions. First: Do jurors understand and apply the criminal mental state categories the way that the widely influential Model Penal Code (MPC) assumes? Second: If not, what can be done about it?
In prior work we challenged numerous assumptions underlying the use of the MPC mental state architecture, which divides guilty minds into four kinds: purposeful, knowing, reckless, and negligent. Our experiments showed that subjects had profound difficulty categorizing some of the mental states, particularly recklessness. And, when asked to punish, subjects punished knowing crimes and reckless crimes indistinguishably. (“Sorting Guilty Minds,” 86 NYU Law Review 1306 (2011) at
The new experiments we describe here extend those prior findings in important ways. For example, we reveal the degree to which a person’s ability to grasp and apply the MPC mental states is susceptible to variations in the language used to define and communicate them. Specifically, our results demonstrate that exactly how the legal system communicates the mens rea criteria is surprisingly crucial.
The extreme sensitivity of subjects to the language of mens rea may have troubling implications for past defendants, as well as for future ones. Because even small changes in phrasing can produce significant differences in juror evaluation of criminal cases, substantial miscarriages of justice may ensue. Our results consequently suggest the need for a critical reexamination of the substantial divide between the expectations and assumptions of the MPC, on one hand, and empirical reality, on the other. This divide is especially meaningful and worrisome given the unparalleled influence of the MPC in our state and federal criminal codes.
Richard J. Bonnie et al., The Language of Mens Rea, 67 Vanderbilt Law Review, 1327–1372 (2014).