Insanity
Insanity: at the time of the act, ∆'s mental disease or defect prevented ∆ from forming the required mens rea or appreciating the wrongfulness of the conduct.
Tests
- M'Naughten Rule (cognitive test, CL majority):
- ∆ did not know the nature and quality of the act, OR
- ∆ did not know the act was wrong.
- See M'Naughten's Case, 8 Eng. Rep. 718 (H.L. 1843).
- Irresistible Impulse Test (volitional supplement):
- ∆ knew the act was wrong, but a mental disease prevented ∆ from controlling the conduct.
- Durham / "Product" Test (rare): the act was the product of mental disease.
- MPC § 4.01 (Substantial Capacity Test):
- ∆ lacked substantial capacity to:
- Appreciate the criminality (or wrongfulness) of conduct, OR
- Conform conduct to the requirements of law.
- ∆ lacked substantial capacity to:
- Federal Insanity Defense Reform Act (1984): ∆ unable to appreciate the nature/quality or wrongfulness, due to severe mental disease/defect (cognitive only; volitional prong abolished post-Hinckley).
Procedure
- Affirmative defense; burden often on ∆ (sometimes by clear and convincing evidence).
- Successful insanity defense usually results in commitment, not release.
Distinct from Competency
- Insanity = mental state at time of crime.
- Competency = mental state at time of trial (whether ∆ can understand proceedings and assist counsel).