What is the test for finding a defendant mentally incompetent to stand trial?

A defendant who is mentally incompetent cannot be tried or adjudged to punishment. ( 1367, subd. (a); Pate v. Robinson (1966) 383 U.S. 375, 378, 86 S.Ct. 836, 838, 15 L.Ed.2d 815.) A defendant is mentally incompetent to stand trial if, as a result of mental disorder or developmental disability, the defendant is "unable to understand the nature of the criminal proceedings or to assist counsel in the conduct of a defense in a rational manner." ( 1367, subd. (a).) The defendant has the burden of proving incompetency by a preponderance of the evidence. ( 1369, subd. (f); People v. Medina (1990) 51 Cal.3d 870, 881-886, 274 Cal.Rptr. 849, 799 P.2d 1282.)

Page 100

[931 P.2d 278] Defendant contends there is insufficient evidence to support the jury's verdict finding him competent to stand trial. Citing People v. Samuel (1981) 29 Cal.3d 489, 174 Cal.Rptr. 684, 629 P.2d 485, defendant argues that a judgment of conviction must be reversed when there is "persuasive and virtually uncontradicted" evidence of a defendant's mental incompetence (id. at p. 506, 174 Cal.Rptr. 684, 629 P.2d 485). We agree. He then asserts that the evidence in this case, in which unanimous expert testimony was contradicted only by lay testimony, is "persuasive and virtually uncontradicted" evidence of mental incompetency. We disagree.