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Insanity Defense


Insanity defense is used by defendants who have committed crimes to defend themselves as they commit the crimes without knowing whether it is right or wrong. This is because the defendant may be having a mental illness or defect that affects him thus being unable to distinguish the right and wrong things.

 History of insanity defense

The idea of use of insanity defense by a criminal has been used in Anglo American law for along time. A legal treatise has been used to differentiate people who understand good or evil and those who do not(Bergman, & Barrett,2008)  The distinction has further been elaborated by the British courts as it has identified the distinction between people who understand good and evil and these who do not. The British court has developed the wild beast test. This test is aimed at defending people who are not sure of their action because of insanity. If a defendant is not sane and he does not understand the results of his behavior he should not be held responsible. The laws for evaluating insanity in British courts have been established in the case of Daniel M’Naughten .

Daniel is said to have murdered the prime ministers secretary instead of murdering the prime minister. But Daniel is said to be influenced by personal and financial misfortune to commit the crime. This is according to the testimony by the witnesses in his case. The witnesses have insisted that he is insane and the court finds him not to be guilty. This case has led to the development of insanity defense in England (Cole, &Smith, 2006).As the court has supported Daniel saying that a defendant should not be held responsible for committing a crime if the defendant cannot tell if his action of committing the crime is wrong. M’Naughten law has been embraced in American courts and it has been used for almost hundred years in the American courts. Other countries have also embraced the M’Naughten rule. Other rules have also contributed to developed of insanity defense. These rules include the irresistible rule which is developed to replace the M’Naughten law and the Durham rule (Fersch, 2005).

 Use of Insanity defense

Insanity defense is said to be defense by excuse. In insanity defense the defendants argue that they should not be held responsible for committing a crime as they are legally insane at the time of committing the crime’s (Fersch, 2005).Defendant using insanity defense is required to undergo mental examination so as to establish if he is really insane. When insanity defense is used in court and it becomes successful the defendant is taken to a psychiatric hospital. In the United States the insanity defense is associated with a mitigating factor called diminished capacity. Mitigating factors are things that are not considered worth for insanity defense like intoxication which leads to reduced charges and sentences. Insanity defense is used in most criminal courts that respect the human rights and have a rule to follow when using insanity defense. The application of insanity defense differs from one court to another as the countries have different rules to be used for insanity defense. Forensic experts examine the use of insanity defense by a criminal as they are able to identify if the defendant is said to be having difficulties of identifying what is good and bad during the time of the crime (Cole, &Smith, 2006).

 Insanity defense is used mostly in many countries. The courts in these countries allow the defendant to defend himself from committing a crime by claiming that he was not sane when he committed the crime (Cole, &Smith, 2006).The defendants use insanity defense from different perspectives. Some courts use cognitive insanity. In this type of insanity the defendant should be impaired by a mental disease or defect during the time of committing a crime. This impairment makes the defendant not to be aware of the nature and quality of the crime he is committing. The court views the defendant to be innocent as they consider him to unaware if the crime is wrong. Most of the countries allow defendants to use cognitive insanity to defend themselves. Other countries apply the insanity defense by using the irresistible impulse.

In this rule the court assumes that the defendant knows what is right and wrong during the crime but he has a mental defect or disease that makes him incapable of controlling his action and then he ends up committing the crime. This defense is used in crimes of vengeance. This kind of defense is not used in most of countries. The use of insanity defense reveals the notion that people who are not able to appreciate the consequences of their action are not required to be punished for their crimes. Most of the countries have established mechanism that governs the use of insanity defense but a few of the countries allow the court to develop rules for using insanity defense. Insanity defense is used in court if the judge instructs the jury to consider if the defendant committed the crime while insane (Bergman, & Barrett, 2008) .The insanity defense is used after the defendant has produced evidence to support the theory. This evidence includes recommendation from psychologists and psychiatrists and also evidence from the forensic experts who identify if the defendant committed the crime while innocent. The judges then decide whether to use the insanity defense.

The use of insanity defense in the court has caused a lot of problems as many people do not support the idea as they see the rules being lenient to people who have committed crime. The public claims that people who commit crime may use the insanity defense so as to escape the crime while people who are not guilty may end up being tried as they are not allowed to use the insanity defense (Barlow, & Durand, 2008).This has raised a lot of concern in many countries on whether to use the rule or not. Most of the countries have abolished the use of insanity defense as the rule sounds unfair to most of the people. This is because people who have committed murder and other big crimes may appear innocent before the court through the use of the insanity defense. These defendants commit this kind of crimes through the use of drugs that affect them psychologically and this makes the criminal not guilty before the court. Others belief that the use of insanity defense in courts has used information from psychiatrists and psychologists more thus concentrating more on mental illness but not on the crime( Barlow,& Durand,2008).


Insanity defense has been used in most of the countries but it has raised a lot of issues.This is because the public thinks that the insanity rule is an escape for people who have committed bigger crimes. The history of insanity defense is as a result of the M’Naughten law, the irresistible impulse, the Durham and other laws. Different countries have used these laws to enhance insanity defense among the defendants.


Barlow, D., &Durand, V. (2008).Abnormal Psychology: An Integrative Approach.Edition5.Cengage Learning, page 563

Bergman, P., & Barrett, S. (2008).The Criminal Law Handbook: Know Your Rights, Survive the System.Edition10.Nolo, page 312

Cole, G., &Smith, C. (2006).The American System of Criminal Justice.Edition11.Cengage Learning, page 126

Fersch, E. (2005).Thinking about the Insanity Defense.iUniverse, page 11-123


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