The mental defect can be called a “defect of reason” or a “disease of the mind,” depending on the jurisdiction (Iowa Code, 2010). First, the defendant must be suffering from a mental defect at the time he or she commits the criminal act. The M’Naghten insanity defense is cognitive and focuses on the defendant’s awareness, rather than the ability to control conduct. After a public outcry at this verdict, the British House of Lords developed a test for insanity that remains relatively intact today.
M’Naghten was put on trial for murder and, to the shock of the nation, the jury found him not guilty by reason of insanity (Queen v. When he tried to shoot Sir Peel from behind, he inadvertently shot Sir Peel’s Secretary, Edward Drummond, who thereafter died. M’Naghten was under the paranoid delusion that the Prime Minister of England, Sir Robert Peel, was trying to kill him. The defense is named after Daniel M’Naghten. It is also the oldest and was created in England in 1843. The M’Naghten insanity defense, also called the right-wrong test, is the most common insanity defense in the United States. Thus no deterrent effect is served by punishment, and treatment for the mental defect is the appropriate remedy.įour variations of the insanity defense currently exist: M’Naghten, irresistible impulse, substantial capacity, and Durham. 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. Second, an insane defendant does not have the ability to form criminal intent. This is similar to a defendant who is hypnotized, or sleepwalking. First, an insane defendant does not have control over his or her conduct. The policy supporting the insanity defense is twofold. Thus the defendant’s conduct is not excused if the defendant or society can benefit from punishment. While the purpose of a medical diagnosis is to eventually cure the defendant’s disorder, the purpose of criminal law is to punish the defendant. Criminal prosecution should deter as well as incapacitate. The rationale behind creating a different standard for legal insanity is the goal of a criminal prosecution discussed in Chapter 1 “Introduction to Criminal Law”. However, legal insanity differs from medical insanity and is generally much more difficult to establish. Often, mental disturbance is apparent from the defendant’s conduct under the circumstances. Many criminal defendants suffer from mental illness and can produce evidence of this illness such as psychiatric or layperson testimony. This is generally because of the difficulty in proving legal insanity. However, the insanity defense is rarely used and hardly ever successful. 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. Montana, Utah, Kansas, and Idaho are the only states that do not (, 2010). 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.Īlthough controversial, most states and the federal government recognize an insanity defense (18 U.S.C., 2010). This chapter reviews criminal defenses based on excuse, including the insanity defense. With the exception of alibi and the expiration of the statute of limitations, Chapter 5 “Criminal Defenses, Part 1” explored criminal defenses based on justification. Distinguish temporary from permanent insanity.Compare different commitment procedures for an insane criminal defendant.Compare the insanity defense with the guilty but mentally ill verdict.Compare the insanity defense with mental competence to stand trial.Distinguish between diminished capacity and the insanity defense.Identify the various burdens of proof for the insanity defense.Ascertain the basis of the Durham insanity defense.Compare the M’Naghten, irresistible impulse, and substantial capacity tests.
Ascertain the two elements required for the irresistible impulse insanity defense.Ascertain the two elements required for the M’Naghten insanity defense.