--- - |2 Abstract Criminal responsibility in the American legal system requires the presence of an actus reus—a harmful act that was committed voluntarily—and a mens rea, or guilty mind. Courts frequently consider questions surrounding mens rea but rarely question whether an act was committed voluntarily. Thus, courts presume that acts have been committed voluntarily and with an ill will; retribution, which serves the primary basis for punishment in the USA, relies on this presumption. Research in neuroscience and the behavioral sciences, however, suggests that this presumption is flawed and not sufficiently robust to justify punishment that is grounded in retribution. In this paper we discuss the presumption of voluntariness and free will inherent in the law, provide examples of how the courts have conflated actus reus and mens rea and the consequences of doing so, and the implications of neuroscience and behavioral science research for actus reus (also known as the voluntary act requirement). Finally, we propose re‐conceptualizing punishment within a consequentialist, empirically‐based framework that does not rely on folk psychological notions about human behavior and reinvigorates the actus reus as the foundational requirement for legal responsibility. - Behavioral Sciences & the Law, Volume 36, Issue 4, Page 426-436, July/August 2018.