Criminal Justice- Major Tests for Insanity

Major Tests of Insanity

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The criminal justice procedure exempts criminals from full penalty on account that a defendant claims and proves that the criminal acts committed were due to temporary or permanent insanity. In legal terms, the word insanity is defined as a medical illness or defect (Bing, 1996). However, this description is not tantamount to the medical definition of insanity, which relates to having a mental disease or disorder. Accordingly, the court has to perform tests of insanity to prove whether the defendant is insane before punishment or acquittal.

This paper presents a discussion of the four major tests of insanity employed in criminal justice. The paper compares and contrasts these four tests and gives a recommendation of which test is best suited to determine insanity.

The Four Tests of Insanity

In criminal law, a mentally ill person is not necessarily legally insane and vice versa. For that reason, tests have to be carried out to determine whether the accused is insane or not so as to know how to pass judgment. Four major tests of insanity have been applied to determine insanity including the Federal Test, Irresistible Impulse Test, M’Naghten Test, and the Model Penal Code Test.

Enacted in 1984, the Federal Test states that a defendant can be excused from his crimes if, at the time of committing the offence, he was suffering from a severe mental disease which caused him to have complete cognitive incapacity (Bing, 1996). Simply put, the defendant needs to prove that his mental disease resulted in him not realizing what he was doing or the wrongfulness of his acts.

The Irresistible Impulse Test, on the other hand, states that a person can claim to be insane if, when committing the offence, he acted from uncontrollable impulse and could not choose between right and wrong acts. In essence, this test argues insanity on the lines of mental illness that affects volitional capacity (Bing, 1996).

Comparable with the Irresistible Impulse Test, The M’Naghten Test looks at insanity as a mental illness that causes cognitive disability (Bing, 1996). This test states that a person can be deemed as legally insane of at the time of committing the crime he suffered a disease of the mind, which caused the person not to know the nature of the criminal act committed.

Lastly, the Model Penal Code Test states that a person can be considered as being legally insane if, when committing the act of crime, this person did not have substantial capacity to understand that his acts were criminal or to abide by the rules of the law about committing that crime.

Out of the four insanity tests used, the best and most appropriate insanity test is the M’Naghten test. This is because, this test demands that the defendant prove to be suffering from complete cognitive disability and does not recognize incapacity as a cause for insanity. Claiming that a defendant was incapable of recognizing his crime or controlling his impulse or abide by the rules of law is not substantial enough to declare insanity. This is because; it is quite easy for a defendant to argue out that they were incapable to recognize the crime committed even if they are not legally insane. For that reason, the M’Naghten test is the only test that can really prove if a person is insane or not, thus allowing the court to give a merited ruling over the case.



Bing, J. L. (1996). “Protecting the Mentally Retarded from Capital Punishment: State Efforts

Since Penry and Recommendations for the Future.” New York University Review of Law and Social Change, 22.