LEARNING OBJECTIVES
- Identify four states that do not recognize an insanity defense.
- Identify four versions of the insanity defense.
- Ascertain the two elements required for the M’Naghten insanity defense.
- Ascertain the two elements required for the irresistible impulse insanity defense.
- Compare the M’Naghten, irresistible impulse, and substantial capacity tests.
- Ascertain the basis of the Durham insanity defense.
- Identify the various burdens o f proof for the insanity defense.
- Distinguish between diminished capacity and the insanity defense.
- Compare the insanity defense with mental competence to stand trial.
- Compare the insanity defense with the guilty but mentally ill verdict.
- Compare different commitment procedures for an insane criminal defendant.
- Distinguish temporary from permanent insanity.
With the exception of alibi and the expiration of the statute of limitations, explored criminal defenses based on justification. This chapter reviews criminal defenses based on excuse, including the insanity defense. Remember that defenses based on excuse focus on the defendant and claim that the defendant should be excused from criminal responsibility for his or her conduct under the circumstances.
Although controversial, most states and the federal government recognize an insanity defense. 1 Montana, Utah, Kansas, and Idaho are the only states that do not. 2 The insanity defense is the subject of much debate because it excuses even the most evil and abhorrent conduct, and in many jurisdictions, legal insanity functions as a perfect defense resulting in acquittal. However, the insanity defense is rarely used and hardly ever successful. This is generally because of the difficulty in proving legal insanity.
Many criminal defendants suffer from mental illness and can produce evidence of this illness such as psychiatric o r layperson testimony. Often, mental disturbance is apparent from the defendant’s conduct under the circumstances. However, legal insanity differs from medical insanity and is generally much more difficult to establish. The rationale behind creating a different standard for legal insanity is the goal of a criminal prosecution discussed in . Criminal prosecution should deter as well as incapacitate. While the purpose of a medical diagnosis is to eventually curethe defendant’s disorder, the purpose of criminal law is to punish the defendant. Thus the defendant’s conduct is not excused if the defendant or society can benefit from punishment.
The policy supporting the insanity defense is twofold. First, an insane defendant does not have control over his or her conduct. This is similar to a defendant who is hypnotized, or sleepwalking. Second, an insane defendant does not have the ability to form criminal intent. Without the ability to control conduct, or the understanding that conduct is evil or wrong by society’s standards, an insane defendant presumably will commit crimes again and again. Thus no deterrent effect is served by punishment, and treatment for the mental defect is the appropriate remedy.
Four variations of the insanity defense currently exist: M’Naghten, irresistible impulse, substantial capacity, and Durham.
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