§ 16.01   Generally

 

"Diminished capacity" refers to a defendant’s abnormal mental condition, short of insanity.  There are two forms of diminished capacity:  mens rea diminished capacity and "partial responsibility" diminished capacity.

 

§ 16.02   Mens rea Defense

 

[A]  General Rule – Evidence of mental abnormality is not offered by the defendant to partially or fully excuse his conduct, but rather as evidence to negate an element of the crime charged, almost always the mens rea element.  In such circumstances, diminished capacity thus functions as a failure-of-proof defense.

 

[B]  Scope of Defense – States are divided regarding the extent to which evidence of diminished capacity may be introduced for the purpose of negating the mens rea of an offense. States that follow the Model Penal Code [§ 4.02(1)] permit such evidence, when relevant, to negate the mens rea of any crime. Other states limit the admissibility of such evidence to some or all specific-intent offenses. A third group bars "diminished capacity" evidence in prosecutions of all offenses.  And some jurisdictions bar "diminished capacity" evidence in all prosecutions whether the crime at issue is "specific intent" or "general intent."

 

§ 16.03   "Partial Responsibility" Defense

 

[A]  General Rule – This form of diminished capacity partially excuses or mitigates a defendant’s guilt even if he has the requisite mens rea for the crime.  It is recognized now in only a few states, and only for the crime of murder, to mitigate the homicide to manslaughter.

 

[B]  The Model Penal Code Approach – The Model Penal Code provides that a homicide that would otherwise constitute murder is manslaughter if it is committed as the result of "extreme mental or emotional disturbance for which there is a reasonable explanation or excuse." The reasonableness of the defendant’s explanation or excuse for the "extreme mental or emotional disturbance" (EMED) is "determined from the viewpoint of a person in the defendant’s situation under the circumstances as he believes them to be."[MPC § 210.3(1)(b)]  At least two states appear to recognize the latter version of the defense.