Author

Because punishable guilt requires that bad thoughts accompany bad acts, the
Model Penal Code (MPC) typically requires that jurors infer the mental state of a
criminal defendant at the time the crime was committed. Specifically, jurors must
sort the defendant’s mental state into one of four specific categories—purposeful,
knowing, reckless, or negligent—which will in turn define both the nature of the
crime and the degree of the punishment. The MPC therefore assumes that ordinary
people naturally sort mental states into these four categories with a high degree of
accuracy, or at least that they can reliably do so when properly instructed. It also
assumes that ordinary people will order these categories of mental state, by
increasing amount of punishment, in the same severity hierarchy that the MPC
prescribes.
The MPC, now turning fifty years old, has previously escaped the scrutiny of comprehensive
empirical research on these assumptions underlying its culpability architecture.
Our new empirical studies, reported here, find that most of the mens rea
assumptions embedded in the MPC are reasonably accurate as a behavioral matter.
Even without the aid of the MPC definitions, subjects were able to distinguish regularly
and accurately among purposeful, negligent, and blameless conduct.
However, our subjects failed to distinguish reliably between knowing and reckless conduct. This failure can have significant sentencing consequences for certain
crimes, especially homicide.