Duhaime's Law Dictionary

Moral Insanity Definition:

A disease of the mind in which the individual is bereft of ethical judgment or feelings but still fully functioning intellectually.

Related Terms: Sociopath, Psychopath

A sometimes-used term to describe the condition of mind of what is now known as a sociopath or a pychopath but also, as it jhas been proposed,  a temporary state of mind such as a fit of rage, anger or jealousy that defeats a person's will.1

The concept of moral insanity has befuddled both the psychiatric and legal professions for decades. The law has been unable to present anything satisfactory. For example, consider that proposed by James Ballantine in his 1960 book, to the effect that moral insanity is a "mental disease as destroys the ability to distinguish between right and wrong in a particular act; a perversion of the moral sense."

An influential medical definition of moral insanity was published by James Prichard in his 1835 book A Treatise on Insanity and Other Disorders Affecting the Mind:

"(Moral insanity is) a form of mental derangement in which the intellectual faculties appear to have sustained little or no injury, while the disorder is manifested principally or alone, in the state of the feelings, temper, or habits.

"In cases of this description the moral and active principles of the mind are strangely perverted and depraved; the power of self-government is lost or greatly impaired; and the individual is found to be incapable, not of talking or reasoning upon any subject proposed to him, for this he will often do with great shrewdness and volubility, but of conducting himself with decency and propriety in the business of life...."

moral insanityBut as Nicole Rafter later wrote:

"American psychiatrists eventually rejected the concept of moral insanity.... Some fretted that moral insanity might become a stepping-stone for criminals hoping to evade justice"

In the courts, wrote Justice Schauer in the 1959 case of People v. Nash

"Moral insanity is now as well understood by medico- jurists, and almost as well established by judicial recognition, as the intellectual form, but ... in our courts of law there is no such doctrine established or recognized as moral insanity, distinguished from mental derangement, as an excuse for crime...

"Moral insanity, as an independent state, is not recognized by law as a defense to crime, and does not constitute such insanity as is a legal defense. Moral insanity, in itself, is not a bar to responsibility for criminal acts; hence, howsoever perverted, if at all, the feelings, conscience, affections and sentiments of a person may be, unless the intellectual faculties and reasoning powers are so affected by mental disease as to render him incapable of distinguishing between right and wrong in relation to the act with which he is charged, he is responsible to the law for his criminal acts."

In People v Skinner (1985) Justice Grodin was presented with the concept of moral insanity and disposed of it as follows:

"Cases subsequent to (1864) accept inability to appreciate moral wrong as a component of the California test of legal insanity.... (A then) correct statement of the law (would be that) an instruction that insanity did not encompass moral perversion of a defendant who knew that the deed is a criminal act, and wrong in itself; (one case) rejecting moral perversion as an acceptable test because a defendant might commit serious crimes "and know at the time that the deed is a criminal act, and wrong in itself," and yet escape punishment.)

"Thus, although it has long been held that moral insanity, arising from a perverted moral sense and brought on by mental illness, is not legal insanity, ... our cases repeatedly distinguish awareness that an act is wrong from knowledge of its legal effect, i.e., that it is unlawful. If the defendant had sufficient mental capacity to appreciate the nature of her act; if she knew and understood that she was violating the rights of another by an act which was in itself wrong, and which was prohibited by the law, and the commission of which would entail punishment upon herself .... she is responsible to the law ... regardless of any perversion of the moral senses, however, great."


  • NOTE 1: McWilliams v Neill, 155 SW 2d 344 (Arkansas, 1941)
  • People v. Nash, 52 Cal. 2d 36 (1959)
  • People v. Skinner, 704 P. 2d 752 (1985)
  • Prichard, James C., A Treatise on Insanity and Other Disorders Affecting the Mind (London: Sherwood, Gilbert and Piper, 1863)
  • Rafter, Nicole, Unrepentant Horse-Slasher: Moral Insanity and the Origins of Criminological Thought, 42 Criminology 979 (2004)
  • Spratling, W. P., Moral Insanity, 8 Medico-Legal J. 220 (1890-1891)

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