Criminality in Nigeria: An Analysis on Mental Health and the Defense of Insanity



kehinde Emmanuel Oladele[1]


Mental condition determines actions. Even, it is veracious that it’s contributes greatly to the percentage of criminalities in every developed and developing society. The mentally affected wrecked significanthavocswithout a knowledge ofthe damage caused on the victim, whilethe defense of insanity is legallyavailed tothem. question This article attempt to answer the questions on the position of Nigeria laws concerningmental illness and  criminal offence committed by the Mentally and Non mentallyaffectedindividuals in the society.Against this backdrop, the paper highlights mental health being a contributing factor tothe aggravated  rate of Crimes with substantial undertone of legal backings, which is the defense of insanity and it’s elementswithin the purview of Nigeria Laws And Judicial Antecedents without under-emphasizing the proving responsibility expected of, and imposed on the mentally affected in the court room.


Agreeably, the connectionthat exist between the duo[2]is most times misapplied, however, it remains undisputed thatindividuals suffering from mental illness  (consciously or unconsciously)commit mishap cumviolence in the society they live.Furtherance to this, the notion of the general public as to a psychiatric patients is being as dangerous individuals is often rooted in the portrayal of criminals in the media as “crazy” individuals.  However, A significantpercentage of  data has over the time  submit otherwise, that the mentally affected individuals in the society are more likely to be a victim of violent crime than the perpetrator[3] This  is to the  extent of a situation where persons with mental illness is falsely punished after being  charged,  consequentially jailed for an undeserved longer time, comparatively, in the general population[4] this is sad and still against the sanity of our laws.Arguments abounds as regards whether psychiatric illness or just a societal moral judgment has occurred. In the contrary, the label is increasingly used to paint criminals as victims of psychiatric illness because it’s a guise of escaping legal punishment for criminality[5], the complimenting accomplice of this wrongfulness is the plea or defense of insanity which is in sequence explained in this article.

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Criminal responsibility guidelines for a  defendants claiming to be insane as at when the offense was committed weremeticulously stipulated by the English Court in the celebrated case ofMcNaughten of which rules were formulated with current applicability [6]Although  the decision in Durham v United States of America[7] wherethe court held that the proper test of criminal responsibility was that an accused was not criminally responsible if his unlawful act was the product of mental disease or mental defect” has nowlimited the scope of the McNaughten[8] which outlined the legal test to determine whether a defendant was legally insane when they committed a crime, andit requires that the defendant either did not know what they were doing or did not know that what they were doing was wrong when they committed the criminal act. Nevertheless, it is noteworthy that mental illnesses could impair the uncertainty of being victimized, this implies that mentally affected individuals experience higher rates of victimization than the general population (Teplin, McClelland, Abram, & Weiner, 2005; Maniglio, 2009), plausibly because their symptoms make them vulnerable.

In Nigeria criminal jurisprudence,the defense of insanity is always raised in this both circumstances, whether mentally affected or not, it’s left for the Court to decides. Now, The definition of the word insanity is very nebulous and contested, it is incapable of precise definition. The Black`s Law Dictionary[9][10] described insanity as:

Any mental disorder severe enough that it prevents a person from having legal ceapacity and excuses the person from criminal or civil responsibility.

ADefendant who in the court of law during trials, raises the defense of insanity as a Matter of law is required to bring such under one of the conditions stated in Section 28 of the Criminal Code. The section provides[11]:

A person is not criminally responsible for an act or omission if at the time of doing the act or making the omission he is in such a state of mental disease or natural mental infirmity as to deprive him of capacity to understand what he is doing, or of capacity to control his actions, or of capacity to know that he ought not to do the act or make the omission’. This means that the defense must establish that: The moment the three conditions are established and not againstthe defence, the case is in their favor, except these conditions are satisfied, such a defendant would be found guilty and in consequence, be convicted by the court.

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Even, Section 51 of the Penal Code[12]being explained states that there’s nothing like offence if such unlawful acts is committed by reason of unsound mind. The criminal code speaks not only of a mental disease, but also of a natural mental infirmity, which covers wider situations than the term ‘mental disease. Our Courtin R.V. Omoni[13]  in defining ‘natural mental infirmity’ adopted a passage from Stephen’s Digest of criminal law, It is  a defect in mental power neither produced by his own default, nor the result of disease of the mind’. Be that as it may, the Law is not dealing with vanity, our laws are  concerned with serenity and justice In the society, as such,it established the instrumentality of satisfying burden of proof, irrespective of mentally ill or not, the facts on qualified evidence would evidently resolve the matter.


Wali JSC  in Mohammed v State[14]emphasized that, ‘under the Nigerian law, in order to establish a defence of insanity, the defence has to prove that at the relevant time of committing the offence, the accused was suffering either from mental disease or from natural mental infirmity and secondly, that the mental disease was such that at the relevant time, the accused was, as a result, deprived him of the capacity:-

  • To understand what he was doing, or
  • To control his, actions; or
  • To know that he ought not to do the act or make the omission’

The learned justice further highlighted that issues of insanity may arise at two different stages. i.e. before the trial commences, or even during the trial. Buttressing this, it may be manifested where the defendant may be so insane as to be incapable of making his defence. It could also arise where even though the defendant able to make his defence, he may also claim that he was insane at the time he committed the act as not to be criminally responsible. Immediately the judge has reason to suspect, before the commencement or during the course of the trial, that a defendant is of unsound mind, and consequently incapable of making his defence, before proceeding any further, the court must investigate the question, taking such medical evidence as required.


In the Ngene Arum v. The State (1979) 11 SC 91 at 94, Fatayi- Williams CJN(as he then was) expatiated on the disparity between self defense and defense to insanity in this words:

…..‘Thus, if an accused person under the influence of his delusion supposes that another man was going to kill him and he then kills the man believing that he did so in self-defense he would be exempted from punishment for the killing…..

What this accentuates is that to constitute a defence on the ground of insanity, the defect of reason must be shown to be of a particular kind; and it must be qualified to be brought within these three categories, (1) whether the accused know the nature and quality of his act? If not, insanity is a defence; (2) whether he knows the nature and quality of his act, did he know it was wrong? If not, insanity is a defence. See the case of  Dillon v. R (1939) 27 Cr. A.R. at p.152.(3)And, whether he was under a delusion in some other respect? If so, a successful defence of delusion will not completely exonerate the defendant. He is still criminally responsible for the act or omission to the same extent as if the real state of things had been such as he was induced by the delusions to believe to exist. Delusion can not be equivalent to defense of self defense nor the defence of mistake under Section 25 Criminal Code, being that the latter must be honest and reasonable, whereas a delusion, though required to be a genuine one, is patently not reasonable according to our jurisprudence.

Now, a satisfactory defense of insanity would result  in special verdict of ‘not guilty by reason of insanity’ not acquittal. And, a finding of insanity who negate criminal responsibility and the defendant will be kept in a special custody anticipating Governor’spleasure.Section 229 of the CPA states that whena person acquitted by virtue of section 28 or 29 (2) (b) of Criminal Code, trial court verdict as held  shall state specifically whether he committed the act alleged or not. In the circumstance where he committed the act alleged and would have been guilty of an offence but for his insanity, section 230 Criminal Procedure Act then says the president or governor’s pleasure shall be sought.

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The  Supreme Court vividly stated the burden of prove in defense to insanity inGuobadia v State (2004)6 NWLR (PT.869) pg. 360  when it held that, ‘the standard of proof required of the accused in a case of insanity is however, proof on the balance of probability or preponderance of evidence and not proof beyond reasonable doubt, therefore, it’s expected the judge must be satisfied with this, not a proving beyond reasonable doubt as expected in murder case.


In as much as our courts have held that where the natural mental infirmity emanates from the accused’s default, the defence of insanity will not avail the defendantexcept it’s proved. This promptedVerity CJ [15] in R v. Omani toexplain the conflated notion on mental health and societal effects that the ascertainment of Truth or not, doesn’t make it an unresolved concept, that the defense of insanity is properly underregulations. Hence, the presumption of law that every person is of sound mind until the contrary is proved, is trite.  Therefore, It is on this strength that this writer submits conclusively that mental illness though could be defended hasn’t been left without stringent precautionary techniques adopted to ameliorate it’s effects, and the defense of insanity is not a pretext to support criminalities.On the whole, the axiom of wrong beliefs on the thrust of this paper wouldn’t survive, with defense responsibility and burden of proof, manifest cure to injustice shall be realistic andfinallyusher in a new regime of justice.

Thanks for going through this post; An Analysis on Mental Health and the Defense of Insanity.


Aguda, A. T., & I. Okagbue, Principles of Criminal Liability in Nigeria Law, (2nd end. Ibadan: Heinemann Educational Books, 1991).

Aguda, A. T., The Criminal Law and Procedure of the Southern States of Nigeria, (3rd edn, London: Sweet & Maxwell, 1982). Aguda. A. T., The Law of Evidence, (3rd edn. Ibadan: Spectrum Law Publishing; 1992).

Akanki, E. O., Essay on Company Law, (end. Lagos: University of Lagos Press, 1992).

Awogu, F., The defences of insanity, insane delusion and irresistible impulse in Nigerian Criminal Law: being Judicial Lectures on Continuing Education for Judiciary, Organized by Judicial Committee and Continuing Education, Yaba, Lagos (1991).

Ayua, I. A., Law, Justice and the Nigerian Society: Essays in Honour of Hon. Justice Mohammed Bello (end. Lagos: Nigerian Institute of Advanced Studies, 1995).

Baird, N., Criminal Law, (London: Cavendish Publishing Limited, 1993).

Barbara Wooton, Crime and the Criminal Law (London: sweet & Maxwell, Ltd., (1963), p.80

Black, H.C., Black‟s Law Dictionary, (6th edn, St. Paul Minnesota:

Chukkol, K. S., The Law of Crimes in Nigeria, (Zaria: Ahmadu Bello University Press Ltd, 1988).

[1] Legal Writer And Researcher, Analyst, (undergraduate Law Student, ABU ZARIA) +2347033702316.


[3] Watsson A, Hanrahan P, Luchins D, Lurigio A. Mental Health Courts and the complex issues of mentally ill offenders. Psychiatry serv. 2001 Apr;52 (4): 477-81

[4] Gottfried Ed, Christopher SC Mental Disorders Among Criminal Offenders: A Review Of The Literature. J Correct Health Care. 2017 Jul;23(3):336-346

[5]Habersaat S, Ramain J, Mantzouranis G, Palix J, Boonmann C, Fegert JM, Schmeck K, Perler C, Schmid M, Urben S. Substance-use disorders, personality traits, and sex differences in institutionalized adolescents. Am J Drug Alcohol Abuse. 2018;44(6):686-694

[6]1(1843) 8 ER 718

[7]3 214 F2d862 (1954)

[8]In favor of a broader medical Tests and held that an accused is not criminally responsible if his unlawful Act was the product of mental illness. However, the decision in Durham`s case gave rise to criticism and objections and in 1972 a panel of federal judges overturned the decision in Durham`s case in favor of the Model Penal Code test of American Law Institute (A.L.I) which allows for the introduction of medical and psychiatric evidence, together with the introduction of defence of diminishing responsibilities/ capacity to cure manifest injustice many accused persons were exposed to before now in America.

[9] Garner, B., Black`s Law Dictionary (7th Edn, St. paul Minm: Thompson west,

[10] )p.797

[11]Cap C39  Laws of the Federation 2004

[12]   Cap 89 Laws of Northern Nigeria 1963

[13]   R V Omoni (1949) 12 WACA 511

[14](1997) 9 NWLR (PT. 526) 169

[15]“The Nigerian Law being what it is, it may be well to state quite clearly what in our opinion the defence must prove under that law, to establish insanity and to overcome the presumption that every man is sane and accountable for his actions. First it must be shown that the prisoner was, at the relevant time, suffering either from mental disease or from ‘natural mental infirmity’ as we have interpreted its meaning (i.e. a defect in mental power neither produced by his own default nor the result of the disease of the mind). Then it must be established that the mental disease or the natural mental infirmity, as the case may be, was such that, at the relevant time, the prisoner was as a result deprived of capacity: (a) to understand what he was doing; or (b) to control his actions; or (c) to know that he ought not to do the act or make the omission”..

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