The Modern Defense of Insanity

Ono Academic College, Kiryat Ono, Israel


1.1 The Evolution of Insanity as a General Defense in Criminal Law

Two evolutions are involved in shaping insanity as a general defense: medical and legal. The medical evolution reflects developments in the understanding of the phenomenon of mental disorders; the legal evolution reflects the elaboration of the social consequences of insanity in daily situations. Both evolutions are discussed below.

1.1.1 The Medical Evolution: Religion vs. Science

The first known attempt to classify mental disorders was in ancient Egypt, toward the end of the forth millennium bc.1 This classification had to do mostly with the concept of religious sin, with the gods punishing the sinner by having an evil spirit take control over his soul.2 In monotheistic religions it is believed that mental disorder is the punishment for a person’s sins, therefore it makes no sense to explore the nature of the mental disorder to seek a cure.3 No person is allowed to countermand God’s will, as expressed by the person’s mental disorder. It is how God wished it to be.

Although a few scholars objected to this religious concept, it prevailed in all spheres of life and society until the mid-1700s. Consequently, not only was there no incentive to intervene in the divine punishment, but the religious institution used the cases of mental disorder in order to deter the population from becoming potential sinners. Naturally, redemption was possible only through absolute belief in God. But the stubborn people persisted in their heresy, and therefore God did not cure their mental disorder.

By the mid-1700s, new attitudes toward mental disorder had evolved. These attitudes were not based on the religious concept of sin and punishment, and therefore mental disorder was no longer considered divine punishment.4 Pioneering research in the field documented the symptoms of various types of mental disorders and attempted to classify them according to symptoms. Ironically, because of the depth of religious belief, the main beneficiaries of this research were religious leaders and clerics who used the results to deter believers from sinning by exposing the variety of divine punishment.5

When society or the family sought treatment for a specific mental disorder, no physician was called for help or advice sought because the issue was not considered to be a medical one. In general, the objective of the treatment was to ease suffering, and the “treatment” was religious.6 The reason was considered to be obvious. Dealing with mental disorder required communication with the supernatural world, and the professionals who dealt with mental disorders were not physicians but priests.7 Physicians dealt exclusively with physical ailments, not mental ones.

In 1775, Franz Mesmer, a German physician, made the first attempt to explain mental disease using the medical terms of “animal magnetism.”8 Mesmer argued that an invisible liquid with strong magnetic properties is present in the universe, holds the stars in place, and affects human health. He advocated treatment with magnets to cure mental disease by balancing the patients’ personal magnetic properties. This was a crucial point in the development of psychiatry. From this point onward, scholars considered mental disease as a human rather than a religious matter, and psychiatry became part of the medical science.

Two main trends developed in psychiatry. The first one identified the causes of mental illness as physical, having to do with the physical state of the brain.9 The second one identified them as emotional in nature, affecting the feelings of the mentally ill person.10 According to the second trend, people were diagnosed to be mentally ill if their feelings and volition were not balanced. The diagnosis was made by a physician who specialized in treating mental illness.

In 1835, James Prichard, an English physician, developed the term “moral insanity,” which encompassed two main situations. The first was one of moral disorientation, when the person was incapable of understanding what was the moral way to act in certain situations. The second was one of deficient moral judgment, when people held mistaken concepts about the moral way to act, although they were aware of common moral values.11 The deficient moral judgment was manifest primarily as a deviation from common conduct, especially in a sexual context. The accepted concept was that immoral sexual conduct can cause insanity.12 Naturally, moral sexual conduct was consistent with Victorian values of human behavior.

By the end of the nineteenth century, these trends and attitudes, including the notion of moral insanity, had faded under strong religious American influence. Americans were concerned that medical developments in the area of insanity may harm the religious beliefs, moral standards, and legal praxis in the United States.13 American scholars preferred the traditional and satisfactory explanations of insanity as divine punishment for sinners. This influence originated in the United States and dominated research in this field until the late 1970s.14

The American influence has led legislators and scholars to oppose a general defense of insanity in criminal law. The American influence did not extent to Europe, however. By the end of the nineteenth century, scientific research in psychiatry, centered in Europe, had become much more accurate, marking a renaissance of psychiatry and the birth of modern psychiatry. Around that time, in Europe, the first rational model of mental illness was developed by Emil Kraepelin, the first scientific theory of schizophrenia was proposed by Eugen Bleuler, the first neurological model of psychiatry was developed by John Jackson, and many other models were put firth by various researches.

Various fields and sub-fields of psychiatry emerged at the same time. These fields included the psychology of sexuality, psychopathology, the study of dreams, and the study of the subconscious, under the influence of Sigmund Freud. In this way modern psychiatry began to consolidate.15 One of the most significant branches of the modern psychiatry was dynamic psychiatry, which sharply criticized the theological models of human behavior, the theories of supernatural powers dominating human nature and the human mind, and naturally, the religious belief that insanity is a divine punishment for religious sins.16

The critique initiated by modern dynamic psychiatry followed parallel developments in the fields of criminology and penology, especially serving the development of rehabilitation as a legitimate consideration in sentencing offenders.17 These developments had obvious and derivative significance for criminal liability and criminal law. But although the different branches of modern psychiatry criticized the theological and religious explanations of insanity in similar ways, they lacked similar concepts, insights, or attitudes toward the proper ways of treating mental illness and disorders. These branches proposed different explanations for the essence, and consequently the proper treatment, of mental illness.

For example, the distinction between physical and mental psychiatry originated in the two main trends of psychiatry that existed at the end of the eighteenth century, a distinction that remains relevant to this day. The different branches of psychiatry explain differently the etiology of mental illness and propose different solutions for curing it.18 Although new trends in modern psychiatry reject earlier explanations and solutions, and new methods replace old ones, the psychiatric discourse is a scientific one, based on scientific developments. Therefore, psychiatric insights into mental illness are subject to scientific developments in that field, which affect also the legal evolution of insanity.

1.1.2 Legal Evolution: The Interplay Between the M’Naghten Rules and the Irresistible Impulse Test

The legal evolution of insanity, especially as a general defense in criminal law, was not isolated from its medical evolution. Some crucial points in the legal evolution were influenced and encouraged by the medical evolution. Under Roman law, it was not acceptable to impose criminal liability upon the mentally ill, and in certain circumstances of public danger, mentally ill persons were held in public custody, not in order to cure them or treat their illness, but to keep them away from the public and prevent potential harm to society.19 The custody was not considered punishment, but a cautionary measure to protect society.

By the twelfth century, courts in Europe pointed out the need for a general and accurate theory that accounts for the essence of insanity in order to exempt insane offenders from criminal liability.20 This approach was probably the consequence of the academic legal studies in the new European institutions called “universities.” Legal academic studies required a general scientific methodology, which had to address the issue of insanity as well. The legal examination of insanity did not require an understanding of the reasons for insanity, only the identification of its overt symptoms, in order to determine the extent of the criminal liability of the offender.

Theories of criminal law have spawned various legal indicators and tests used to identify insane offenders in order to determine their criminal liability. These indicators reflect the social, religious, theological, and medical developments in the area of insanity. By the mid-nineteenth century, three main tests were developed to legally diagnose the insane offender, to be replaced in 1843 in England by the M’Naghten rules. The three tests were:


the good and evil test;



the wild beast test; and



the right and wrong test.


The good and evil test appeared for the first time in 1313 in English common law.21 The offender in that case was under the age of seven, which was the minimal age for imposing criminal liability under English common law. The test reflected Medieval theological concepts regarding mental illness. Mentally ill persons, like infants, were considered incapable of committing sins because they were not capable of free will in their condition. Consequently, these offenders lacked the capability to distinguish between good and evil, and could not choose between the two of their own free will.22

The terminology of the good and evil test is theological, derived primarily from the biblical story of the original sin and the expulsion from Eden.23 The exemption from criminal liability of the insane offender was based on the concept that insanity was in itself a punishment and satisfied the necessity to punish offender. Additional punishment was considered double punishment, and therefore it was not acceptable.24 This was the prevailing test in the English common law between the fourteenth and the eighteenth centuries.25 During that time, English courts needed a concrete way to examine the capability of the offender to distinguish between good and evil. Therefore, in 1616 the test was redefined to refer to persons who were not capable of counting from 1 to 20, who did not understand the quantity implied by the number 20, who did not recognize their parents, or did not distinguish between useful and harmful matters. Such persons were considered “idiots,” unless they were able to read and write.26 An offender who has been identified as an idiot was not considered to have legal personhood, and therefore was not subject to the imposition of criminal liability.

Without a basic understanding of the moral value of the conduct it was not possible to impose criminal liability, but in practice only extreme cases of insanity passed the test. Most cases, as understood at the time, were not accepted as insanity.27 The good and evil test was modified from time to time by the courts in order to fit the factual reality and developments in the understanding insanity, and in 1724 it was replaced by the wild beast test.

To apply the wild beast test, the judge instructed the jury to exonerate the offender for reason of insanity if it was found that he did not understand his conduct and behaved no better than a wild beast. Such a person did not deserve punishment under criminal law.28 This test was a combination of seventeenth century doctrines regarding criminal liability and religious attitudes towards insanity, which prevailed in England in those days. Indeed, the term “wild beast” was a mistranslation of the original Latin term “brutis” (brutes), from the thirteenth century, when the concept was enunciated by the English jurist, Bracton.29

This term did not appear before in any description of insanity. At the beginning of the eighteenth century, “wild beast” referred mostly to livestock and to animals of the meadow such as badgers, foxes, dear, and rabbits.30 The wild beast test raised the criteria for being considered insane, reducing the rate of acceptance of the insanity defense in criminal cases. The test emphasized the cognitive capabilities of the offender rather than his impulses, as its name might imply.31

The test prevailed in English common law until 1812, when it was replaced by the right and wrong test, which was the most significant step toward the M’Naghten rules, adopted in 1843. According to the right and wrong test, the insanity defense could not be accepted, if the offender had adequate understanding to distinguish between right and wrong or good and evil.32 Because the terms good and evil were too vague to be interpreted, the courts preferred right and wrong as sole criterion for the test.33 The principal difference between the wild beast and the right and wrong tests was that the latter abandoned all moral standards affected by religion in favor of the legal standards of right and wrong.

These standards were not based on moral understanding but on broad definitions of criminal offenses. “Wrong” parallels “forbidden” by the law, and “right” parallels “allowed.” Criminal offenses define the borderline between what is legally right and wrong, so that the function of the court is to determine whether the offender understood the prohibition. This test opened wider opportunities for an insanity defense, and it was criticized for not embracing the medical developments of insanity.34 The test prevailed in English courts until 1843.

On January 20, 1843 Daniel M’Naghten (or McNaughton) shot Edward Drummond, the private secretary of the British Prime Minister, Robert Peel, intending to assassinate the Prime Minister. Drummond was wounded and died 5 days later. M’Naghten suffered from symptoms of paranoia and believed that he was persecuted by the Tory party. The court of first instance heard testimonies of experts in mental illnesses in order to understand the mental capabilities of the offender.35 The court understood that acquitting the offender would result in his being placed in a psychiatric hospital because he was dangerous to the public.

At the end of the trial, the court acquitted M’Naghten for reason of insanity based on the right and wrong test, provoking a sharp debate in Britain. With the encouragement of Queen Victoria, a special session of the House of Lords was convened. The House of Lords presented to the Court five questions to determine the effect of insanity on the imposition of criminal liability. The answers of the Court amount to the M’Naghten rules, which are considered to be the modern legal basis for the insanity defense in criminal law. The five questions were36:


What is the law respecting alleged crimes committed by persons afflicted with insane delusion, in respect of one or more particular subjects or persons: as, for instance, where at the time of the commission of the alleged crime, the accused knew he was acting contrary to law, but did the act complained of with a view, under the influence of insane delusion, of redressing or revenging some supposed grievance or injury, or of producing some supposed public benefit?



What are the proper questions to be submitted to the jury, when a person alleged to be afflicted with insane delusion respecting one or more particular subjects or persons, is charged with the commission of a crime (murder, for example), and insanity is set up as a defence?



In what terms ought the question to be left to the jury, as to the prisoner’s state of mind at the time when the act was committed?



If a person under an insane delusion as to existing facts, commits an offence in consequence thereof, is he thereby excused?



Can a medical man conversant with the disease of insanity, who never saw the prisoner previously to the trial, but who was present during the whole trial and the examination of all the witnesses, be asked his opinion as to the state of the prisoner’s mind at the time of the commission of the alleged crime, or his opinion whether the prisoner was conscious at the time of doing the act, that he was acting contrary to law, or whether he was labouring under any and what delusion at the time?


The answer of the Court to the first question was: “[t]he first question, as I understand it, is, in effect, what is the law respecting the alleged crime, when at the time of the commission of it, the accused knew he was acting contrary to the law, but did the act with a view, under the influence of insane delusion, of redressing or revenging some supposed grievance or injury, or of producing some supposed public benefit? If I were to understand this question according to the strict meaning of its terms, it would require, in order to answer it, a solution of all questions of law which could arise on the circumstances stated in the question, either by explicitly stating and answering such questions, or by stating some principles or rules which would suffice for their solution. I am quite unable to do so, and, indeed, doubt whether it be possible to be done; and therefore request to be permitted to answer the question only so far as it comprehends the question, whether a person, circumstanced as stated in the question, is, for that reason only, to be found not guilty of a crime respecting which the question of his guilt has been duly raised in a criminal proceeding? And I am of opinion that he is not.

There is no law, that I am aware of, that makes persons in the state described in the question not responsible for their criminal acts. To render a person irresponsible for crime on account of unsoundness of mind, the unsoundness should, according to the law as it has long been understood and held, be such as rendered him incapable of knowing right from wrong. The terms used in the question cannot be said (with reference only to the usage of language) to be equivalent to a description of this kind and degree of unsoundness of mind. If the state described in the question be one which involves or is necessarily connected with such an unsoundness, this is not a matter of law but of physiology, and not of that obvious and familiar kind as to be inferred without proof”.37

The answer of the Court to the second question was: “[s]econd, the questions necessarily to be submitted to the jury, are those questions of fact which are raised on the record. In a criminal trial, the question commonly is, whether the accused be guilty or not guilty: but, in order to assist the jury in coming to a right conclusion on this necessary and ultimate question, it is usual and proper to submit such subordinate or intermediate questions, as the course which the trial has taken may have made it convenient to direct their attention to. What those questions are, and the manner of submitting them, is a matter of discretion for the Judge: a discretion to be guided by a consideration of all the circumstances attending the inquiry. In performing this duty, it is sometimes necessary or convenient to inform the jury as to the law; and if, on a trial such as is suggested in the question, he should have occasion to state what kind and degree of insanity would amount to a defence, it should be stated conformably to what I have mentioned in my answer to the first question, as being, in my opinion, the law on this subject”.38

The answer of the Court to the third question was: “[t]hird, there are no terms which the Judge is by law required to use. They should not be inconsistent with the law as above stated, but should be such as, in the discretion of the Judge, are proper to assist the jury in coming to a right conclusion as to the guilt of the accused”.39 The answer of the Court to the fourth question was included in the first answer.40

The answer of the Court to the fifth question was: “[f]ifth, whether a question can be asked, depends, ‘not merely on the questions of fact raised on the record, but on the course of the cause at the time it is proposed to ask it; and the state of an inquiry as to the guilt of a person charged with a crime, and defended on the ground of insanity, may be such, that such a question as either of those suggested, is proper to be asked and answered, though the witness has never seen the person before the trial, and though he has merely been present and heard the witnesses: these circumstances, of his never having seen the person before, and of his having merely been present at the trial, not being necessarily sufficient, as it seems to me, to exclude the lawfulness of a question which is otherwise lawful; though I will not say that an inquiry might not be in such a state, as that these circumstances should have such an effect”.41

Thus, under the M’Naghten rules, criminal liability is imposed on the offender even if he committed the offense in a state of insanity as long as he was aware of the criminal prohibition while he was committing the offense. The court presumes the offender sane unless otherwise is proven. The insanity must relate to the time when the offense was committed, and it refers to the cognitive capability of the offender to distinguish between right and wrong. The criminal liability is imposed only based on the subjective understanding of the factual situation by the offender, including a factual mistake. Medical reports may be relevant only if the question before the court is medical.

The M’Naghten rules formed the legal basis for the insanity defense in the Anglo-American legal systems,42 but the terms used in these rules were not clear enough to be interpreted by the lawyers. After the M’Naghten rules were adopted, mental illness was interpreted narrowly, and it referred mostly to specific types of psychosis.43 Later it was interpreted more broadly, to include other mental disorders, among them other types of psychosis, neurosis, and even very low IQ, as long as it could be identified as the cause for the offender’s inability to understand the difference between right and wrong.44

This legal situation does not reduce the definition of insanity to certain types of mental disorders or mental phenomena, but it examines the effect of given mental disorder on the understanding of individual persons of the difference between what is legally right and wrong. Thus, when the functional effect of the mental disorder is emphasized, significant types of mental disorder would not be classified as insanity under criminal law because the M’Naghten rules require a causal relation between the mental disorder and the inability to distinguish between right and wrong.45

The factual causal relation is at the heart of the M’Naghten rules and the basis for accepting insanity as a defense in a given criminal trial. The ability to distinguish between right and wrong was interpreted to relate to the cognitive abilities of the offender to understand properly the legal social control system in a given society. These abilities may be summed up as awareness of the general meaning of a criminal prohibition.46 In most Anglo-American courts, these cognitive abilities were interpreted as the offender’s ability to understand the nature of his conduct and its quality in light of the criminal prohibition.47

The general understanding of the offender that his conduct represents the commission of an offense is the key term in determining insanity under the M’Naghten rules. If the offender lacks these cognitive abilities he is considered insane under the substantive criminal law, and incompetent to stand trial (non compos mentis) under procedural criminal law.48

The key term “wrong,” which refers to the criminal prohibition, was not easily interpreted after M’Naghten. It was asked whether it refers to the legal or to the moral meaning of the prohibition.49 For example, the offender who sets fire to a brothel under the delusion that he is commanded by God to do so in order to advance his redemption, he is fully aware of the criminal prohibition against setting the fire. The offender understands that his conduct is legally prohibited, but he considers it to be morally commendable. The M’Naghten rules did not explicitly interpret which type of “wrong” the court must address: the legal or the moral one. English common law preferred the legal meaning over the moral one,50 and American courts have left the decision to the jury,51 so that at times the wrong is legal and at others it is moral.52

The M’Naghten rules also address the factual mistake doctrine. Factual mistake functions as independent defense in criminal law, irrespective of what caused it. Naturally, the cause may be insanity, but not necessarily. Insanity may make it easier to prove factual mistake, but it is not necessary for such a proof. The reference the M’Naghten rules make to medical reports is not only for cases of insanity, but applies to any expert report. According to the rules of evidentiary law, such a report is admissible only if it refers to the one of the factual issues raised in the trial.

The M’Naghten rules were criticized primarily for three reasons. The first was that the rules are based on archaic insights and perspectives, no longer in use. Mental disorder is not considered to affect only the cognitive capabilities of the person but all aspects of human personality, including volition and feelings, which in most cases are also involved in delinquency.53 The second reason was that the rules are not sufficiently accurate to identify the individuals on whom no criminal liability should be imposed. The general distinction between right and wrong does not satisfy this purpose.54 The third reason was that the questions presented in M’Naghten rules were not answerable by psychiatrists or expert physicians. The distinction between right and wrong is not a medical matter, at least not only a medical matter, and it involves deep understanding of social sciences, philosophy, and more.55 In light of this criticism of the M’Naghten rules, various changes were suggested, some slight, others quite comprehensive.

To answer the first critique, it has been suggested to expand the legal definition of insanity beyond the cognitive elements, as understood based on the M’Naghten rules. The suggestion was to add a parallel test to the M’Naghten rules, which is not restricted to the cognitive aspects of insanity; it has come to be known as the irresistible impulse test, focused on the volitional aspects of the human mind. Thus, if mental disorder produced uncontrollable conduct, it should be legally valid as an insanity defense.56 The irresistible impulse test was not based on the cognitive understanding of the criminal prohibition. Insanity based on the irresistible impulse test was accepted by the courts as a defense against the imposition of criminal liability even if the offender understood the factual reality, distinguished between right and wrong, and was fully aware of the wrongfulness of his conduct. Therefore, in various legal systems the irresistible impulse test has led courts to accept the insanity defense in cases of uncontrollable will or feelings even if the alleged mental disorder did not affect directly the cognitive aspects of the offender’s mind.

The irresistible impulse test was considered to supplement the M’Naghten rules with regard to the principle of fault in criminal law. Whereas the M’Naghten rules related to the cognitive aspects of the human mind, the irresistible impulse test related to volition, resembling the structure of the principle of fault in criminal law, as discussed below.57

The irresistible impulse test, however, is based on earlier rulings than the M’Naghten rules,58 and some courts have used it before the M’Naghten rules were formulated. Three years before M’Naghten, an English court in Oxford handed down a ruling based on insane volition.59 The Oxford case was not mentioned in M’Naghten probably because delusions were considered to affect human cognition rather than volition, and Daniel M’Naghten suffered from delusions. The court in M’Naghten seems to have considered the irresistible impulse test to be irrelevant to its case. But because of the wide acceptance of the M’Naghten rules, the irresistible impulse test was rejected in the English common law, and considered “most dangerous.”60

The reappearance of the irresistible impulse test was due only to the criticism of the M’Naghten rules for abandoning the volition aspects of the human mind. Embracing the irresistible impulse test together with the M’Naghten rules was possible because of some adjustments in the original test for the M’Naghten rules. Thus, it was required that the irresistible impulse be derived from a mental illness, and that the impulse be of sufficiently high degree to nullify the free choice of the offender to decide whether or not to commit the offense, even if the impulse was not accidental or temporary, but permanent and foreseeable by the offender.61

In practice, this “adjustment” deviates from the literal meaning of the term “impulse.” Most impulses are neither permanent nor foreseeable, but this interpretation fits many of the symptoms of mental illness that affect the volition of the human mind.62 A general criticism of the adjusted irresistible impulse test and of its legal combination with the M’Naghten rules focuses on the uncontrollable character of the conduct, which is the consequence of mental illness. In general, complete loss of control over the volition of the offender was required to pass the test. When the loss of control is not complete, the irresistible impulse test does not qualify the offender as insane.63

Thus, the criticism of the M’Naghten rules was that the test restricts insanity to a minority of the cases, and to the rarest ones.64 By contrast, it was argued that the irresistible impulse test widens excessively the boundaries of the insanity defense. Therefore, it was regarded to be more suitable as a consideration in sentencing the offender rather than in determining his criminal liability, because it includes some indirect ingredients of the distinction between right and wrong.65 This argument was too robust to be ignored, and therefore some courts preferred not to apply the test as a basis for accepting the insanity defense.66 Application of the irresistible impulse test was not considered to reduce the level of deterrence in criminal law.67

Because of the general criticism of the M’Naghten rules and of the irresistible impulse test, various legal systems adopted different attitudes toward these tests and their combination. American law accepted the criticism of the M’Naghten rules and of the irresistible impulse entirely. In 1871, the M’Naghten rules were fully rejected, together with the irresistible impulse test, in a New Hampshire ruling owing to the above criticism. A new indicator for insanity was established, according to which, if commission of the offense was the product of mental illness, the offender was exempt from criminal liability.68 This general indicator was not accepted outside New Hampshire,69 but in the meantime, until 1954, American courts did not consider themselves as bound by the M’Naghten rules of by the irresistible impulse test.

In 1954, the New Hampshire indicator was used to fill the vacuum resulting from the rejection of the M’Naghten rules and of the irresistible impulse test.70 The ruling was that no criminal liability is imposed on any offender if commission of the offense was the product of any “mental disease or defect.” This indicator, destined to replace the much criticized combination of the M’Naghten rules and the irresistible impulse test, offers an adequate theoretical alternative. But the courts did not interpret the relevant terms included in the alternative, which consequently became vague and too flexible.

The alternative indicator determined no guidelines for recognizing mental diseases or defects. Therefore, it is possible to infer that any slight mental defect can become the basis for an exemption from criminal liability for reason of insanity. Furthermore, the term “product” was not interpreted either, leading to the question whether any product may be considered a “product” in this context. If, for example, the commission of the offense is a by-product of various phenomena, only one of which, even a secondary one, is a mental defect, is it considered to be an adequate basis for the insanity defense?

As a result, this alternative was criticized by both lawyers and psychiatrists.71 The main criticism focused on the fact that the terms “mental disease or defect” and “product” were not defined. In individual cases, the courts attempted to interpret these terms,72 but eventually, the alternative was rejected entirely in 1972 because of this criticism.73 The American Law Institute Model Penal Code proposed using the M’Naghten rules together with the irresistible impulse test, with a slight rephrasing concerning the substantial capacity of the offender.74

The principal elements of the M’Naghten rules were incorporated into the Model Penal Code under the test for evaluating the criminality of the offender’s conduct using the terms of the right and wrong test. The significant elements of the irresistible impulse test were also accepted under the alternative for determining whether the offender’s conduct conforms to the requirements of law. The Model Penal Code proposal, designed to provide an adequate answer to both the cognitive and volitive aspects of the mental defect, was embraced by various courts across the United States.75

The United States Congress accepted a test based on the M’Naghten rules in 1984 as part of its legislation.76 Thus, both the M’Naghten rules and the irresistible impulse test, with the slight rephrasing, are now the conclusive test for the acceptability of the insanity defense in American criminal law.77

In Britain, the M’Naghten rules remain the legal basis for the acceptance of the insanity defense in criminal law. Although in Britain mentally deficient offenders plea diminished responsibility rather than insanity, the defense is still widely used in British courts. The irresistible impulse test has been rejected in Britain as “most dangerous,”78 therefore insanity is examined only in relation to its cognitive aspects. The volition aspects of insanity are not considered legitimate criteria for the acceptance of the insanity defense.

The legal debate in Britain over the insanity defense parallels the discussion about the mental element requirement.79 This attitude is consistent with the legal understanding that the mental element is the positive aspect of the principle of fault, and insanity is part of its negative aspect, as discussed below.80 A favorable court ruling on an insanity defense is considered a legal rather than a medical ruling.81 In general, English law any mental deficiency may be considered insanity for purposes of the application of the M’Naghten rules, if it interferes with the offender’s ability to make the distinction between right and wrong.82

In France, the insanity defense applies to any mental or neurologic deficiency, if it denies the offender the capability to distinguish between right and wrong or prevents physical control over his conduct.83 There is no restriction to specific types of mental deficiency. Thus, factual causation is required between the mental or neurologic deficiency and the commission of the offense. The French law emphasizes the free choice of the offender with regard to the commission of the offense.

An offender who commits an offense in a state of insanity is considered to be coerced and not having a free choice as to whether or not to commit the offense, therefore it is not legal to impose criminal liability on him. The coercion, in this case, is internal and its cause is mental.84 The insanity test references the time of the commission of the offense, not to the time of the trial.

In Germany, insanity is an integral part of the offender’s fault. The presumption of insanity is explicitly stated in the German Penal Code.85 This presumption negates the offender’s fault if all conditions are met, leaving two possible options: that no criminal liability is imposed or that diminished responsibility is attributed to the offender.86

The conclusive test for insanity in German criminal law is whether the offender is mentally capable of understanding the prohibition breached by his conduct. The relevant prohibition is legal, not moral or other. Inability to understand the prohibition is the result of a pathologic mental or cognitive deficiency, of mental illness, or of volitive deficiency.87 Thus, German criminal law is open to all plausible causes for insanity, which is examined dynamically and subjectively for the individual offender.88

In sum, the legal evolution of insanity as a general defense in criminal law may be described as an interplay between the M’Naghten rules and the irresistible impulse test. This interplay delineates an approach toward insanity that combines both the cognitive and volitive aspects of the human mind. Deviation from this combination is rare, and generally both aspects play a role in the legal definition of insanity.

1.2 What Is Insanity? Defining Insanity Internally

To use the insanity defense in criminal law, it is essential to be able to define insanity. The definition of insanity rests on two foundations: an internal and an external one.89 The internal foundation considers insanity an isolated phenomenon, whereas the external one considers boundaries of insanity in relation to other tangential defenses. Both are necessary to form the matrix of insanity. The internal foundation of the definition applies to social, medical, and legal insanity.

1.2.1 The Relativity of Social Normality

To understand what insanity is, we must make a detour into the social understanding of normality. Most people consider a person insane relatively to themselves or to other so-called normal people. If a standard normal person could be described accurately, this could form the basis for a comparison between any individual person and normality. But inevitably questions arise: Who is a normal person? How is normality defined? Or more radically, are there any normal people? Can normality be defined at all?

People use the expression “normal” when referring to human behavior that is not considered exceptional from their point of view. Certain groups of people may share a common view of what is exceptional behavior. But there is no generally accepted definition for exceptionality. Various societies and cultures, at different times, may develop different points of view in this regard. For example, talking to invisible spirits may be considered normal in some religious societies, but abnormal in others.

Nevertheless, that which is exceptional is not necessarily banned or oppressed. It would be inaccurate and simplistic to divide all possible types of human behavior into normal and abnormal. A more accurate division includes at least three categories: normal, above-normal, and sub-normal (Fig. 1.1).90


Fig. 1.1
The range of normality

In the above scheme, the two outside ranges are infinite and form the borderlines of the middle range. Both above-normality and sub-normality are infinite and may include infinite types of human behavior, even exceeding the “normal” imagination. The key difference between above-normality and sub-normality is not necessarily intrinsic, but a function of the way the society treats the two: the abnormality of above-normality is generally encouraged, whereas that of sub-normality is generally deprecated. Two mothers meet with their children’s elementary school teacher. One is told that her child is a mathematical genius, far ahead of her biological age. The other is told that her child is exceedingly nervous and violent, much beyond his age.

Both children are outside the range of normality, but in most modern societies the first mother would be advised how to encourage her daughter’s abnormality, whereas the other would be advised how to repress that of her boy. These recommendations are entirely dependent on the prevalent views of society and the given time. The exceptionally aggressive boy may have been categorized as above-normal in ancient Sparta and encouraged to develop his tendencies into a professional skill, whereas the mathematical skills of the young girl may have resulted in her being declared a witch in some mediaeval societies. The skills are the same, but the societies in which they manifest are different. Therefore, normality is a social matter, dependent on time and culture rather than on the chemistry of the brain.

Similarly, there is no assurance that what is currently considered sub-normal behavior will not be categorized normal or even above-normal in the future. Various normal and above-normal behaviors in the past would definitely be categorized sub-normal today, and some would even require exclusion from society on grounds of dangerousness. It would be instructive to reexamine some model behaviors of past cultural heroes based on the current understanding of normality in most Western societies.

People who claim to hear voices that others cannot hear, and that these voices command them to take certain actions, are generally referred to psychiatric evaluation. In most cases, they would be classified as abnormal, and therefore insane. These people match the profiles of most of the ancient prophets, whom modern Western society tends to admire, teach their prophecies, and even learn about their ways. Nevertheless, some of their acts would be classified as criminal offenses under modern criminal law, and people committing these acts today would be excluded from society. The Biblical character of Abraham is a good example.91

Abraham heard voices that others couldn’t hear, commanding him to kill his son. He obeyed these voices, committing what in modern criminal law would be called attempted murder.92 Under modern criminal law, the courts would have to protect society from such persons. What made Abraham into a cultural hero was the combination of the time and society in which his acts were committed. The Bible supplies many such examples, as well as examples of the opposite nature. In biblical times, people who favored the voice of logic were not necessarily considered heroes.

For example, King Ahaz, who reigned over Judea between 733 and 727 bc, faced an invasion by enemies. Rather than accepting the dangerous advice of one prophet to fight the enemies alone, he chose to call on the Assyrian Empire for help, saving Judea from devastation. At the end of his reign, King Ahaz left Judea stronger than before his reign, in control of larger territories. But the biblical narrator considers King Ahaz as sinner for being reasonable, whereas the prophet who claimed to have heard the voices that Ahaz refused to heed is considered a cultural hero.93

It is puzzling that although times and cultures have changed, people worldwide still consider some of the past heroes as cultural models to this day, despite the fact that today many would have been referred to psychiatric evaluation and separated from society. The answer to this puzzle may have to do with the collective memory of society, in which past understandings, attitudes, and insights passed from one generation to the next are accumulated.

Even when the general attitude of society toward such cases has changed entirely, the interpretation of the past may still remain unchanged, not unlike the way children remember adults. The child usually remembers an adult as a giant. After many years of not seeing that adult, the grown-up child of yore is surprised that the adult is in reality much shorter than imagined, but even after discovering the true height of the adult, the image of the adult as a giant is still difficult to supplant. It is interesting, however, that it is much easier to cross from sub-normality to beyond-normality and from beyond-normality to sub-normality rather than to cross from each of them to normality. That may reflect that most societies make small changes in their understandings of normality in comparison to dramatic changes through time in their understandings towards abnormality.

The ambivalent attitude of modern society toward the abnormal heroes of the past may be one of the reasons for the complicated present approaches to abnormality. In some cases, the analogy with heroes of the past would be expected to raise doubts in the judges’ minds regarding the insanity of the offender. The more attached society is to its past culture, the easier it should be for its judges to recall the past heroes. In traditional cultures, this can be a crucial factor in the assessment of insanity.

The key question is how abnormality is reflected in insanity. Clearly, not all cases of abnormality are automatically classified as insanity. Moreover, abnormality and normality are not inclusive or total. A person’s behavior may be classified as normal in one aspect and abnormal in another, and similarly, it may be classified sub-normal at one respect and above-normal in another. For example, some autistic persons have extremely high powers of concentration and analysis of detailed information. At the same time, they experience difficulties in creating social connections. Both characteristics are considered abnormal, but one is above-normal and the other sub-normal.

It is not accurate, therefore, to classify the person in general as normal, above-normal, or sub-normal, but rather particular behaviors should be classified as such. Thus, a person who hears voices may behave normally in every other respect, so that the terms normal and abnormal would not be sufficiently accurate to describe the person, but would be accurate enough to describe his behavior. Naturally, the accuracy must be considered within the range of social norms, i.e., society would consider the behavior to be normal or abnormal based on the concrete circumstances surrounding the matter at hand.

The social meaning of insanity is not some monovalent abnormality or sub-normality. First, not all abnormality or sub-normality is automatically considered insanity. Second, the reason of abnormality is inherent in the classification. Neither a mathematical genius nor an extremely aggressive person is necessarily insane. Nevertheless, because normality is not part of insanity, the connection between normality and insanity is essential but not sufficient.

If a person behaves “normally” based on how society defines normality, he is not within the spectrum of insanity. Even if he suffers from a mental deficiency, as long as it does not affect his behavior to the extent that it exceeds the boundaries of normality, he cannot be considered insane. This classification is purely social, regardless of any medical diagnosis. For example, a person who hears voices but has trained himself to ignore them would not be considered abnormal because his behavior is not affected by the mental deficiency. The public interest is raised only when behavior exceeds the range of normality.

Is any deviation from normality a form of insanity? If the exceptional behavior is encouraged by society, the public interest is not aroused and no criminal liability is contemplated. Thus, only when the deviation is within the sub-normality range may the abnormality be relevant to insanity. And only when the abnormality is the result of problematic behavior, based on the perspective of society, is it considered an object for social intervention by means of criminal law. Otherwise, there is no public interest in initiating such a process.

Every society defines its own range of sub-normal behavior that requires intervention. That range is relative to the fundamental social values in effect in a given society. For example, cheating may be deemed sub-normal behavior in certain societies, but only some types of cheating may be considered subject to social intervention. In most Western societies, cheating the tax system is considered to justify intervention, but not cheating on one’s spouse.

The sub-normality used to assess insanity is not measured by the degree that the behavior exhibits, lest any commission of a severe offense is classified as insanity. Sub-normality refers to the routine mental processes of a person. Murdering a business competitor is not necessarily the result of insanity, but murdering that competitor because the murderer thinks he has the divine right to kill anyone interfering with his activities may be considered insanity in its social meaning. Raping a woman because of sexual lust is generally not considered insanity, but doing so because the rapist thinks that this is the proper way to treat a woman may be considered insanity.

Exceeding normality is an essential condition for insanity, but not a sufficient one. The cause for the abnormality must be mental or internal. If the manner in which the person understands factual reality because of mental deficiency affects his behavior and brings it into the abnormal range, the conditions for social insanity are met. Otherwise, the behavior may be the result of a simple factual error. A mental deficiency affects the way in which the person understands factual reality in general, which may constitute the main difference between factual mistake and insanity as general defenses.

Consider a person charged with rape. The defense claims that the offender had thought the intercourse was consensual. If this error is circumstantial, owing to particular facts, it may be considered a factual mistake but not insanity. But if the offender in general does not accept the possibility of anyone refusing to have sexual relations with him, insanity may be considered. First, it is necessary to examine whether the behavior is within the range of abnormality. If in the given society men are wooed extensively, and sexual offers by men are seldom refused, such behavior may not necessarily be abnormal.

Next, if the behavior is classified as abnormal, its cause is examined. If the cause is mental, insanity may be relevant. Different societies may have different definitions for what is considered to be a mental cause or mental deficiency, as discussed above.94 The mental cause may have to do with both cognition and volition, and the different balance of the two in the definitions of the mental cause in different societies reflects the significant social aspect of insanity.

Therefore, the range of normality is relative. This relativity is measured in social terms, and any society may have different ranges of normality, bounded by different borderlines. As a result, abnormality is also relative. Different societies may consider the same types of behavior as normal, above-normal, or sub-normal. Given that abnormality is the social trigger for insanity, insanity is also socially relative, defined differently in different societies. This raises two additional questions about the meaning of insanity: is insanity a social phenomenon or medical one, and what classification is relevant for legal purposes?

1.2.2 Medical Insanity vs. Functional Insanity and Their Relevance to Legal Insanity

As discussed above,95 the medical understanding of insanity has begun relatively late. When insanity became a subject for research, medical scholars began to categorize the various symptoms of different types of insanity. This classification served as the basis for psychiatry as a branch of medicine. Today, when a psychiatrist treats a patient, diagnosis of the symptoms is the initial step. Then symptoms are assembled into a wider diagnosis of the mental deficiency or illness of the patient, which in turn makes it possible to apply the right treatment.

By categorizing the symptoms and the mental deficiency, the psychiatrist can benefit from the experience of other psychiatrists, who have already treated patients with the same symptoms. It is the assumption of the medical understanding of insanity that mental deficiency is a medical problem, and that medical problems can be solved by medical means. Thus, at the focus of medical insanity are the chemistry of the brain and other physical descriptions of the patient’s body. In its methodology, this treatment is not substantially different than the medical treatment of influenza.

It is therefore not uncommon to find a solution for insanity based on medications. Although the medications are not intended to cure the mental deficiency, they can be used to balance the mental state of the patient. From the point of view of social insanity, as discussed above,96 medications contain chemicals intended to suppress those characteristics of the patient that are considered to be sub-normal. The chemical suppression is intended to reduce to a minimum all types of behaviors that society or the psychiatrist consider sub-normal. Naturally, psychiatrists from different cultures with different behavioral habits may recommend different medical treatments.

The medical diagnosis is affected by the social understanding of insanity. In general, when behavior falls within the normal range, no psychiatric treatment or medication are considered, regardless of whether or not a person suffers from mental deficiency. The argument applies to all types of mental deficiency, so that if the mental deficiency has some external behavioral symptoms, it is subject to psychiatric treatment. Unrelated to any of the above, people who are aware of mental deficiency that involves no behavioral symptoms can initiate treatment voluntarily, but this is of no concern to criminal law.

Medical insanity is therefore governed by the categorization of symptoms relating to the person’s external behavior. But insanity may have a wider meaning, and we must take into account that the medical understanding of insanity is most likely not complete yet. If psychiatry cannot explain every type of insanity and all mental deficiencies, medical insanity is too narrow a tool for evaluating insanity for legal purposes. If there is even one mental phenomenon that is not properly explained from the medical point of view, medical insanity cannot be the ultimate way of understanding insanity, and psychiatry cannot define insanity for criminal law purposes.

If not psychiatry, what is there to help us define insanity unequivocally? The answer to this question represents the most significant step toward defining legal insanity. If criminal law is concerned with anti-social behavior, legal insanity must be determined based on a person’s behavior. The relevant connection that must be taken into account is the effect of mental deficiency on a person’s behavior as it relates to the criminal sphere. Thus, the determination of insanity for legal purposes is functional and not medical or merely social. The question, therefore, is whether mental deficiency had any effect on the functionality of the person in the commission of the anti-social behavior.

Medical or social analysis may support the understanding of the mental situation of the offender and the severity of the deviation from normality, but the ultimate determination of legal insanity can be achieved only through functional analysis. It is the task of the court to analyze the connection between mental deficiency, if alleged, and the commission of the offense. Every society may choose the relevant aspects of functionality that it is willing to accept under given circumstances for the purpose of determining legal insanity. Therefore, if mental deficiency is shown to have affected a person’s cognition or volition, in most legal systems it can become the basis for legal insanity.97

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