Exploring the Insanity Defense

  • 6 Pages
  • Published On: 2-12-2023

A constant tiff between medical and legal professions occurs from using insanity as a defense which draws a deduction from the limited evidences that, insanity can be regarded as a question of fact which cannot be examined by rigid legal test. A person who is suffering from psychosocial disability cannot and should not be punished for the crime committed by them, since they lack their free will. The insanity defense is based on the pragmatic assumption that a defendant who is suffering from any kind of mental disorder and is hence unable to analyze the gravity of the action/crime committed by them since they are unable to discern right from wrong, hence they cannot be legally accountable for their crime. The insanity defense is considered as one of the primary tools in criminal prosecutions. A contrast can be drawn with an explanation of provocation in which the defendant is responsible but their responsibility is reduced because they suffer from a mental state. Thus, insanity defense can be regarded as a legal concept of crime. However, just suffering from a mental state does not carry sufficient evidence to prove the defendant’s insanity. The defendant has to carry the weight of having to prove their insanity by a “preponderance of the evidence” which is much alike a civil case. Therefore, it gets very difficult to determine and prove legal insanity and it is harder still to provide sufficient evidence in the courtroom or on the day of trial. The insanity defense has a long history, and has evolved after undergoing many tests, a process of trial and error. McNaughton's rules stressed on "understandability of right and wrong" and "intellectual" rather than a moral or affective definition dominated in its formulation. Lack of control and certain impulsive drives or actions had been neglected. If we go by the current understanding of neurological evidences of compulsion and lack of control over sudden urge or impulsive actions, rationality tests without the inclusion of lack of control, seem to be outmoded. Separate "Control determination" rather than the "Rationality determination" by the jurors, has the capacity of improving the accuracy of Juror's categorizations. There is a proposition that Relevance ratio is ideal for 'Evidentiary relevance" and expert testimonies should undergo quality control. With progress in neuroscience, the law may need to do away with or alter some of the current assumptions that it harbors, about the idea of voluntary conduct, which underlies various defenses.

Types of Insanity Defenses:

The four kinds of Insanity defenses that currently exist are: M’Naghten, irresistible impulse, substantial capacity and Durham. M’Naghten: The monumental ruling that created a landmark and thereafter controlled the legal landscape for over a decade was the M’Naghten rule. The defense has been named after Daniel M’Naghten. M’Naghten was under a delusive paranoia that the Prime Minister of England, Sir Robert Peel, was trying to kill him. He tried to shoot Sir Peel from behind, he landed up shooting Sir Peel’s Secretary, Edward Drummond accidentally, who thereafter died. When his family narrated his history of mental illness, presenting the defense of Insanity and after the assessment of evidence (while M’Naghten was in prison), the judge directed the jury by saying that “the question to be determined is, whether at the time the act in question was committed, the prisoner had or had not the use of his understanding , so as to know that he was doing a wrong or wicked act”. The hue and cry of the public after the judgement, which acquitted M’Naghten and sent him to Bethlem hospital, prompted the British House of Lords to develop a test for insanity and it still remains intact till date. This has led to the promulgation of the Lunacy Act of 1845. The act set the ground for the establishment of the Lunacy Commission in which was entrusted with the responsibility of transferring people from prisons to asylums, if need be. This marked a precedent for the court in establishing a defense on the grounds of insanity. The M’Naghten insanity defense is based on the cognitive awareness of the defendant, rather than their ability to control their conduct. The defense requires two elements. Firstly, the defendant must be suffering from a mental illness at the time in which he or she commits the criminal act. The mental defect can be cited “defect of reason” or a “disease of the mind,” based on the jurisdiction . Secondly, the one who is dealing with the details of the case details should find out whether it is because of the mental defect, that the defendant did not know the nature and quality of the criminal act, or that the act was wrong. However, there is no definite meaning of “wrong” under the jurisdiction. For some wrong pertains to “legally wrong” actions. Others define wrong as both “legally and morally” condemnable.

Irresistible impulse: The focus of the irresistible impulse is on the defendant’s cognitive awareness as well as their ability to control their conduct. Although this defense has lost its appeal over the years, for the jurisdictions which still recognize this defense, the first element remains the same as M’Naghten- recognition of the mental illness of the defendant. The second element is that of volition which means that if the defendant is unable to control his/her conduct because of the mental illness, that conduct can be excused even if they don’t understand that the act committed by them is “wrong”.

  1. Queen v. M’Naghten, 8 Eng. Rep. 718 [1843]
  2. Lowa Code, 2010
  3. State v. Crenshaw, 98 Wash. 2d 789, 659 P.2d 488 (1983
  4. State v. Skaggs, 248 S.W.2d 635

The Substantial Capacity Test: The Model Penal Code created this test. Post it’s completion, by 1980, almost half of the states and federal governments adopted this test . The test is defined under the Model Penal Code as “A person is not responsible for criminal conduct if at the time of such conduct as a result of mental disease or defect he lacks substantial capacity either to appreciate the criminality [wrongfulness] of his conduct or to conform his conduct to the requirements of law”. The two elements that have been recognized in this case require them to have a mental defect, and it also merges the cognitive standard with the volitional. The Durham Insanity Defense: New Hampshire is the only country which uses the Durham Insanity Defense, also known as the Durham rule or the product test. The defense set forth in a case like this mentions that “[A]n accused is not criminally responsible if his unlawful act was the product of mental disease or mental defect”. However, the court was unable to give proper definitions for ‘product’, ‘mental disease’ or ‘mental defect’. The applicability of Durham’s defense thus becomes extremely hard and eventually it was rejected by the D.C. Circuit in 1972. This kind of defense rests its base on the principles of proximate causation. There are two elements in this case- the person must have a mental illness and the second adheres to the principle of causation, i.e., if the criminal conduct is caused by a mental disease then it should be excused under such circumstances.

Advantages of Insanity Defense:

For a person suffering from a mental illness this defense acts like a life-saver since it comes to his/her rescue by stating that the person’s state of mind, during the act cannot be gauged. They are unaware of the repercussions that might follow therefore, imposition of such burdensome charges against them would be against basic human moral conscience. In many cases these people are neither charged with any penalty nor with any acquittal, depending on the kind of illness that they are suffering from. In many countries the accused are considered as sub-human. For cases like these the Insanity defense acts like a savior.

  1. State v. White, 60 Wash. 2d 551, 374 P. 2d 942 (1962)
  2. Rolf, C.A., 2010
  3. Model Penal Code 4.01(1)
  4. Durham v. US, 401 U.S. 481 (1971)
  5. U.S. v. Brawner, 471 F.2d 969 1972
Evil or Illness:

The ineffectiveness of the Insanity Defense is proven by its rare use. UK abolished the death penalty a long time back, thus most of the defendants do not choose to rely on the Insanity defense, specifically because there are other defenses which have more favorable outcomes. Research has documented that the plea of insanity increased after the Criminal Procedure (Insanity and Unfitness to Plead) Act 1991, in which many more forms of disposal were included, from just indefinite and indeterminate hospitalisation – as was the case under the Criminal Procedure (Insanity) Act 1964 – to the court attaining discretion (except in murder charges). The insanity defense is closely associated with the defense of diminished responsibility under Section 52 Coroners and Justice Act 2009. Similar to the phrase ‘disease of the mind’ under the M’Naghten Rules, the phrase ‘recognised medical condition’ stands for diminished responsibility. It is capable of including all relevant mental disorders, ranging from ‘psychological’ to ‘physical” conditions’. In its discussion of how the criminal law can be reformed or reframed, with regard to the general defense of insanity, the Law Commission pointed out several loopholes which contributed to the underuse of the defense of insanity. One of them is the problematic distinction which was confirmed in R v Quick between sane and insane automatism. This distinction rests upon the identified legal cause of the automatism claim. If the cause is identified as being external to the accused the appropriate plea is sane automatism whereas, if the legal cause is considered to be internal, the plea is insane automatism (Jr. Richard, 1969). This distinction has both theoretical and practical flaws. The distinction also creates major problems with the sentencing of those who are deemed insane automatons and yet may not suffer from a medically accepted mental disorder.

For a judgement to be fair and ethical, it is important that the criminal responsibility should be ascribed correctly. The societal judgement is reflective through the operation of law. In the light of the above discussion it can be regarded that the insanity defense is redundant in the current scenario

  1. Howe, et. al., op. cit., p.294
What happens if they are not found guilty by reasons of insanity?

In any given case, the presumption goes that the defendant is sane, just like the presumption that they can be innocent. Thus it is important for the defendant claiming insanity, to produce evidence that can refute this presumption. Some states require the prosecution to thereafter prove sanity beyond a reasonable doubt or to a preponderance of evidence. The Code of Criminal Procedure adopts the rule that ''a person accused of crime is presumed by law to be innocent until his guilt is proven beyond a reasonable doubt." The presumption of innocence, as explained by Wigmore-"[T]hat the accused . . . may remain inactive and secure, until the prosecution has taken up its burden and produced evidence .... "Yet in Louisiana if the accused pleads insanity he/she cannot remain inactive but must prove his defense by a preponderance of the evidence (Jr. Richard, 1969).This is an improper shifting of the burden of proof to the accused and is contrary to the presumption of innocence. Defendants who are not found guilty by reason of insanity are rarely allowed to get away without facing any penalty. In most of the cases, they are found languishing within the mental health institutes, sometimes longer than the sentence that they were to serve in prison.


There has been significant weaknesses in the insanity defense, as has been pointed out in the paper. There have also been many significant efforts to make amends. The Butler Committee on Mentally Abnormal Offenders proposed a new verdict of ‘not guilty by reason of mental disorder’ in 1975 which recommended that the defense should be available when mental disorder negated the requisite planning of an offence and in case when the defendant was suffering from a severe mental disorder during the time of actions. Had the proposal been accepted the gross labeling of epileptics and diabetics as insane could have been done away with. The flexibility of disposal created by the1991 Act has been able to turn the insanity defense more adaptable,however, the fact that many are still reluctant to use the defense indicates that perhaps the defense can only be used in exceptional cases.

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  1. Elkins, J.R., and students, 2010

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  1. Morse SJ, Bonnie RJ. (2013) ‘Abolition of the insanity defense violates due process.’ J Am Acad Psychiatry Law. 41:488–95
  2. . Gostin LO, Larry OG.(1977) ‘A Human Condition: The law relating to mentally Abnormal Offenders.’ Vol. 2. MIND;
  3. Neville K. The Insanity Defense: A Comparative Analysis Senior Honors Theses. Paper 244. [Last accessed on 2021 Feb 05]. Available from: https://www.commons.emich.edu/cgi/viewcontent.cgi?article=1219&context=honors .
  4. Akhtar S, Jagawat T. (1944) ‘Plea of insanity as a defense in criminal cases: An update. Indian J Psychiatry’;36:25–9
  5. Ashworth A, Horder J. (2013) ‘Principles of Criminal law’. Oxford, UK: Oxford University Press
  6. State v. DeRance, (1882), 34 La Ann 186
  7. State v. Ardoin (1897)
  8. Mukhiya S (2012) ‘Is the Common Law Defence of Insanity Ineffective in Need of Reform’, Plymouth and Criminal Justice Law Review
  9. Slobogin, C (2000) 'An End to Insanity: Recasting the Role of Mental Illness in Criminal Cases', Virginia Law Review, p.1199.
  10. Williams G.(1961), ‘Criminal Law: The General Part’, p.445

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