Can expert testimony be compelling support for an affirmative defense of insanity?

Specifically, expert mental health testimony could have provided compelling support for an affirmative defense of insanity. Under 18 U.S.C. 17, a defendant may assert an affirmative defense to prosecution where, "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 and quality or the wrongfulness of his acts." The defendant must prove this defense "by clear and convincing evidence." Id.; accord United States v. Ventrilla, 233 F.3d 166, 169 (2d Cir. 2000).