Excuse: Insanity

Pre-M'Naghten history. The development of the insanity defense prior to the mid-nineteenth century tracked both the prevailing scientific and popular concepts of mental illness, "craziness," responsibility, and blameworthiness. In existence since at least the twelfth century, the defense has always aroused more discussion than any other topic of substantive criminal law, despite that fact that there were few insanity pleas entered prior to the mid-eighteenth century. Prior to the 1843 M'Naghten decision, the substantive insanity defense went through three significant stages: the "good and evil" test, the "wild beast" test, and the "right and wrong" test.

"Good and evil." The "good and evil" test apparently first appeared in a 1313 case involving the capacity of a child under the age of seven. The test reflected the moral dogmata of the medieval theological literature. The insane, like children, were incapable of sinning against their will since, according to the research done by Bernard Diamond and a colleague, man's freedom "is restrained in children, in fools, and in the witless who do not have reason whereby they can choose the good from the evil (1233)."

"Wild beast." The "wild beast" test appeared in Rex v. Arnold, an 1812 case in which the defendant had shot and wounded a British Lord in a homicide attempt. Judge Tracy instructed the jury that it should acquit by reason of insanity in the case because "a mad man . . . must be a man that is totally deprived of his understanding and memory, and doth not know what he is doing, no more than a brute, or a wild beast, such a one is never the object of punishment."

The emphasis was on lack of intellectual ability, rather than the violently wild, ravenous beast image that the phrase calls to mind; the test continued to be used until at least 1840.

"Right and wrong." The "right and wrong" test (the true forerunner of M'Naghten) emerged in two 1812 cases; in the second of the two, the jury was charged that it must decide whether the defendant "had sufficient understanding to distinguish good from evil, right from wrong . . ." (Bellingham's Case, pp. 477, 671). The test was expanded upon in 1840 in Regina v. Oxford where the jury was told that it must determine whether the defendant, "from the effect of a diseased mind," knew that the act was wrong, and that the question that must thus be answered was whether "he was quite unaware of the nature, character, and consequences of the act he was committing" (546–47).

Even with these rigid tests in place, the public's perceptions of abuse of the insanity defense differed little from its reactions in the aftermath of the Hinckley acquittal nearly a century and a half later. The public's representatives demanded an "all or nothing" sort of insanity, a conceptualization that has been "peculiarly foreign" to psychiatry since at least the middle of the nineteenth century.

M'Naghten. In 1843, the "most significant case in the history of the insanity defense in England" (Perlin, Jurisprudence, at 79) arose out of the shooting by Daniel M'Naghten of Edward Drummond, the secretary of the man he mistook for his intended victim: Prime Minister Robert Peel. After nine medical witnesses testified that M'Naghten was insane, and after the jury was informed that an insanity acquittal would lead to the defendant's commitment to a psychiatric hospital, M'Naghten was found not guilty by reason of insanity (NGRI).

In response to Queen Victoria's fury over the verdict, the House of Lords asked the Supreme Court of Judicature to answer five questions regarding the insanity law, and the judges' answers to two of these five became the M'Naghten test:

[T]he jurors ought to be told in all cases that every man is presumed to be sane, and to possess a sufficient degree of reason to be responsible for his crimes, until the contrary be proved to their satisfaction; and that to establish a defence on the ground of insanity, it must be clearly proved that, at the time of the committing of the act, the party accused was labouring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing; or, if he did know it, that he did not know he was doing what was wrong (722).

The M'Naghten Rules reflected a theory of responsibility that was outmoded far prior to its adoption, and which bore little resemblance to what was known about the human mind, even at the time of their promulgation. Nonetheless, with almost no exceptions, they were held as sacrosanct by American courts that eagerly embraced this formulation, and codified it as the standard test "with little modification" in virtually all jurisdictions until the middle of the twentieth century.