Hendershott (defendant) was charged with third degree assault for physically attacking his girlfriend. Prior to Hendershott’s trial in county court, the People (plaintiff) filed a motion to exclude evidence that because of a brain disorder, Hendershott lacked the required mens rea of knowingly or recklessly causing bodily injury. The trial court granted the motion to exclude on the ground that Colorado law allowed the admission of evidence of the defendant’s impaired mental condition in cases involving specific intent crimes, but not for general intent crimes such as third degree assault. Hendershott was convicted by the jury, and the district court affirmed. The Supreme Court of Colorado granted certiorari.