Chapter 27 Mental Defenses

• Library: SC Crimes: Elements and Defenses (SCBar) (2021 Ed.)

Chapter 27 Mental Defenses

A. Insanity Overview

A criminal defendant is presumed to be sane; therefore, the State does not need to prove sanity in every case. See State v. Senter, 722 S.E.2d 233, 236 (S.C. Ct. App. 2011). However, once the defendant offers evidence of insanity, the State "no longer enjoys the presumption, but must present evidence to the jury from which the jury could find the defendant sane." Id. at 236 (internal quotations and citation omitted).

South Carolina has two definitions of the insanity defense: one common law and one statutory, which incorporates much of the common law definition. The common law defense comes from the nineteenth century English case M'Naughten's Case. M'Naughten's Case, 8 Eng. Rep, 718 (1843). Under M'Naughten, in order to establish the defense of insanity, the accused must demonstrate that at the time of the act, by virtue of "such a defect of reason, from disease of the mind," that he did not know "the nature and quality of the act he was doing, or if he did know it he did not know he was doing what was wrong."

The statute recognizes the two alternative definitions of insanity but changes the M'Naughten requirement of knowledge to "lacked the capacity to distinguish moral or legal right from moral or legal wrong or to recognize the particular act charged as morally or legally wrong." S.C. Code Ann. § 17-24-10(A).

The key to the insanity defense is the defendant's power "to distinguish right from wrong in the act itself — to recognize the act complained of is either morally or legally wrong." Senter, 722 S.E.2d at 236 (internal quotations and citation omitted). Neither the common law nor the statute recognizes the insanity defense in cases where the accused's volitional abilities have been impaired by a mental disease or defect. See State v. Pittman, 647 S.E.2d 144, 170 (S.C. 2007). The statute codifying "guilty but mentally ill" does, however, incorporate impairment of one's ability to conform his conduct to the law as part of the definition of that defense. S.C. Code Ann. § 17-24-20.

Whether a defendant is competent to stand trial is different from whether a defendant was legally insane at the time of the offense. The issue of whether a defendant is competent to stand trial is a question of whether the defendant has "the capacity to understand the proceedings against him or to assist in his own defense as a result of a lack of mental capacity." S.C. Code Ann. § 44-23-410(A).

1. Affirmative defense; S.C. Code Ann. § 17-24-10

(A) It is an affirmative defense to a prosecution for a crime that, at the time of the commission of the act constituting the offense, the defendant, as a result of mental disease or defect, lacked the capacity to distinguish moral or legal right from moral or legal wrong or to recognize the particular act charged as morally or legally wrong.
(B) The defendant has the burden of proving the defense of insanity by a preponderance of the evidence.
(C) Evidence of a mental disease or defect that is manifested only by repeated criminal or other antisocial conduct is not sufficient to establish the defense of insanity.

2. Statutory Elements

To establish the affirmative defense of insanity, the accused must demonstrate by a preponderance of the evidence:

a. That at the time of the commission of the alleged

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