Insanity Defense: Legal Definition vs Medical Definition

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Insanity defense is an important legal principle in determining whether the accused person should be held legally responsible for his or her actions. A defendant who is found to have been insane at the time of committing a crime may be found to be not guilty of the crime and acquitted of all related charges. However, in the cases, the insanity defense can only result in a reduction of the sentence on the basis that the defendant was insane when committing the crime.

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Therefore, given the significance of this legal concept, it is important to understand its definition and meaning from the perspective of both law and medicine. From a legal point of view, insanity defense is a defense by excuse that is used in criminal proceedings to argue that the defendant cannot be held responsible for their actions because of episodic or persistent psychiatric illness. This definition is founded on various legal principles such as the Durham rule and the M'Naghten Rules and the definition provided for by the American Legal Institute definition as well as other legal definitions that relate to the concept of mens rea or guilty mind. Terms such as defense of mental disorder, not criminally responsible by reason of mental disorder or defense of mental illness are often employed to describe the legal condition of insanity defense. On the other hand, from a medical perspective, insanity defense can only be established by forensic mental health professionals.

Under What Circumstances Is a Person Considered Insane?

In determining whether a person is insane or not, there are several legal principles that are examines. These include The "M'Naghten Rule", The "Irresistible Impulse" Test, The "Durham Rule", The "Model Penal Code" Test for Legal Insanity which are used variedly in different jurisdictions. According to the "M'Naghten Rule", one is considered insane if they either did not comprehend what they did or if they failed to distinguish right from wrong due to a disease that affects the mind.

On the other hand, the "Irresistible Impulse" Test stipulates that a defendant is considered insane only as a result of verifiable mental ailments that made it impossible for the defendant to control his or her impulses, thereby leading to commission of the crime. The Durham Rule states that regardless of the diagnosis of the individual, the mental defect of the defendant can result into a crime. Finally, the "Model Penal Code" Test for Legal Insanity posits that as a result of a mental defect that is diagnosed on the defendant, he or she either failed to comprehend the criminal nature of his actions or that due to the condition, he was unable to act within the confines of the law.

Who Determines of a Person Is Insane?

In order for a person to be considered legally insane for the purposes of determining his culpability in a criminal proceeding, the courts will rely on evidence from a report written by forensic mental health professionals who assess and diagnose the individual.

How Often Is It Used?

Insanity defense is a very controversial legal concept. In the US, controversy surrounding insanity comes from the variances in terms of how it is applied across the states as well as within the federal system. States such as Idaho, Montana, Kansas, and Utah do not allow for insanity defense to be used in criminal proceedings. Most of the states that allow for the insanity defense use either the M'Naghten Rule or the Model Penal Code. The Durham standard is only used in New Hampshire.

Therefore as a result of these variations, the insanity defense is rarely used in legal proceedings. The insanity plea accounts for less that 1% of all the criminal cases in the US criminal justice system. There are some states that have initiated processes to ban their of insanity plea in their jurisdictions.

Nevertheless, there are many numerous prominent cases that involve the insanity defense principle, most of which have resulted in landmark judgments in the US.

What Problems Arise When Trying to Use This Defense?

There are very many challenges that legal practitioners encounter when using the insanity plea. One such challenge is the fact that there are existing differences in terms of how the insanity plea is perceived by mental health professionals and legal professionals. While the legal professionals depend on the opinion of mental health practitioners on heather one is insane, such opinion does not really matter when it comes to making the final judgment since the decision will be made by a jury that may not have a background of psychiatry or psychology. This is a major challenge because the opinion of professionals may not have any impact on the final decision after all. The other challenge is that there is not a lot of information or statistics on the criminal justice system and the mentally ill. For instance, it is not clear what the number of mentally ill people come into contact with the police and how many of those get incarcerated or those that are under community supervision. Such information would make it easier to process cases involving the insanity plea.

Is it usually successful? Why/Why not?There are cases in which the insanity defense has been successful whereas it has been unsuccessful in others. One of the instances where the insanity plea has been successful is the case of Andrea Pia Kennedy Yates from Houston Texas. In 2001 was accused of drowning her five children in a bathtub. She argued that she suffered from serious mental problems including severe postpartum depression and postpartum psychosis at the time of the crime and wanted to use the insanity plea.

The case became very popular among lethal professionals because allowed people to closely scrutinize the M'Naghten Rules with the Irresistible Impulse Test. In her first trial, she confessed to the crime, but pleaded for insanity defense. However, the Texas law demands that for one to assert insanity defense, it has to be proved that he or she could not differentiate right from wrong at the tie of committing the crime. A jury rejected her plea and found her guilty of the crime. The prosecution had asked for a death penalty, but this was also rejected by the jury. She was sentenced by the trial court for life imprisonment with eligibility of parole in 40 years.

However, in 2006, the case took a twist when Dr. Park Dietz, a prosecution witness and a psychologist admitted to giving material false witness in the case. Yates entered her insanity plea one again in January 2006 and was released on bail on February 1, 2006, with a condition that she be admitted to a mental health facility. In July 2006, after three days of deliberations in the court, Yates was found not guilty on the grounds of her insanity as defined by the legal framework in Texas.

What Are the Criticisms of the Insanity Defense?

Insanity defense has been criticized for creating an avenue for criminals to escape punishment on the basis that they were not in the right frame of mind at the time of committing the crime. Besides, the concept is not very well defined in both federal and state law, thereby leaving a lot of grey areas in terms of how it is applied.

Works Cited

Allen, Woody. The Insanity Defense: The Complete Prose. New York: Random House Trade Paperbacks, 2007. Print.

Simon, Rita J, and Heather Ahn-Redding. The Insanity Defense, the World Over. Lanham: Lexington Books, 2008. Print.

Nalepa, Laurie, and Richard Pfefferman. The Murder Mystique: Female Killers and Popular Culture. Santa Barbara, Calif: Praeger, 2013. Print.

Overtree. Andrea Yates. Nov 1, 2007. Web, retrieved from

Andrea Yates. Oct 18, 2009. Web. Retrieved form

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