Murfreesboro defense lawyer

What Is the Insanity Defense?

Published On - August 14, 2018

Stan Bennett Criminal Law

Murfreesboro defense lawyerHaving the bad guy assert the insanity defense is a favorite plot twist to Hollywood blockbusters and bestselling crime novels. It tends to leave everyone on the edge of their seats wondering if he will get away with his crimes. In real life, however, the insanity defense is used much less frequently and is far more difficult to prove than Hollywood has led us all to believe. A Murfreesboro defense lawyer explains some insanity defense basics and how as well as how the defense is used in Tennessee.

Insanity Defense Basics

Because our country operates under a federalist form of government, each individual states determines whether or not an insanity defense exists and, if it does, what the standard is for successfully asserting the defense. As of 2018, four states, (Kansas, Montana, Idaho, and Utah) do not allow the insanity defense at all. In other states,  a defendant may assert an insanity defense; however, the standard for proving the defense varies widely. In addition, states differ as to whether it is considered an affirmative defense or not. An affirmative defense, once asserted, shifts the burden onto the State. States that do allow the insanity defense use some version of the following legal standards:

  • The M’Naghten Rule — focuses on whether a criminal defendant knew the nature of the crime or understood right from wrong at the time it was committed. The defendant must meet one of the two distinct criteria. Some courts differ as to whether the “wrong” in question refers to moral or legal wrong (or both). Additionally, some states have eliminated the first part of the test in which a defendant is ruled legally insane for not fully understanding what he or she has done.
  • The Irresistible Impulse Test — was first adopted by the Alabama Supreme Court in the 1887 case of Parsons v. State. The Alabama court stated that even though the defendant could tell right from wrong, he was subject to “the duress of such mental disease [that] he had … lost the power to choose between right and wrong” and that “his free agency was at the time destroyed,” and thus, “the alleged crime was so connected with such mental disease, in the relation of cause and effect, as to have been the product of it solely.” In so finding, the court assigned responsibility for the crime to the mental illness despite the defendant’s ability to distinguish right from wrong.
  • The Model Penal Code Test — Using the MPC test, a criminal defendant must be found not guilty by reason of insanity if he is diagnosed with a relevant mental defect (for example, severe mental retardation or schizophrenia disorder) and at the time of the incident was unable to either:
    • Appreciate the criminality of his conduct; or
    • Conform his conduct to the requirements of the law
  • The Durham Rule – the broadest of all tests, under the Durham Rule a criminal defendant cannot be convicted of a crime if the act was the result of a mental disease or defect at the time of the incident. It has often been referred to as the “product defect” rule, but does not require a medical diagnosis of mental illness or disorder. The Durham Rule is only used in New Hampshire.

The Insanity Test in Tennessee

The State of Tennessee uses a modified version of the Model Penal Code with regard to the use of the insanity defense. Once asserted as an affirmative defense, the burden shifts to the State. Tennessee Code Section 39-11-501governs the use of the insanity test, reading as follows:

(a)  It is an affirmative defense to prosecution that, at the time of the commission of the acts constituting the offense, the defendant, as a result of a severe mental disease or defect, was unable to appreciate the nature or wrongfulness of the defendant’s acts. Mental disease or defect does not otherwise constitute a defense. The defendant has the burden of proving the defense of insanity by clear and convincing evidence.

(b)  As used in this section, mental disease or defect does not include any abnormality manifested only by repeated criminal or otherwise antisocial conduct.

(c)  No expert witness may testify as to whether the defendant was or was not insane as set forth in subsection (a). Such ultimate issue is a matter for the trier of fact alone.

Contact a Murfreesboro Defense Lawyer

If you have additional questions or concerns about the use of the insanity defense in Tennessee, it is in your best interests to consult with an experienced Murfreesboro criminal defense lawyer at Bennett, Michael & Hornsby as soon as possible. Contact the team today by calling 615-898-1560 to schedule your appointment.

Stan Bennett
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