(a) It shall be an affirmative defense in a trial by court-martial that, at the time of the commission of the acts constituting the offense, the accused, as a result of a severe mental disease or defect, was unable to appreciate the nature and quality or the wrongfulness of his or her acts. Mental disease or defect shall not otherwise constitute a defense.
(b) The accused has the burden of proving the defense as provided for by subsection (a) of this Code section by clear and convincing evidence.
(c) Whenever lack of mental responsibility of the accused with respect to an offense is properly at issue, the military judge shall follow the procedures set forth in Code Section 17-7-131.