Rational capacity and criminal responsibility in the USA

The United States Supreme Court recently found that an insanity defense based upon moral incapacity was not constitutionally required. This decision allows states with a moral incapacity insanity defense, i.e., most states, to abolish their insanity defense. Unfortunately, the Court's opinion was based upon conflated concepts without considering irrationality, traditionally and universally the indispensable core element of insanity standards. This present perspective review attempts to clarify and disambiguate the critical concepts of instrumental and rational capacities as applied to insanity standards. With a proper understanding and application of these distinctly different capacities, insanity standards that at least incorporate rationality should in the future meet the Court's touchstone for determining constitutionally required due process.