For a defendant to be convicted of a crime, the prosecution must prove beyond a reasonable doubt that a criminal act, or actus reus, occurred and that criminal intent, or mens rea, was present. Diminished capacity is a legal defense claiming that a person did not possess the mens rea, or intention of wrongdoing, necessary to be held accountable for committing a crime. This concept is based on the assumption that a medical or mental health disorder, or intoxication with a mind-altering substance, can lead to an altered state of mind rendering someone incapable of cognitively intending to commit the crime.

The rationale for allowing a diminished capacity defense is to prevent those experiencing a temporarily altered state of mind from being held entirely accountable for ...