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

If, as a result of a mental disorder or a developmental disability, the accused is incapable of understanding the nature of the proceedings against him or her and is unable to assist counsel in presenting the defense in a rational manner, then he or she is incompetent to stand trial. (Pen.Code, 1367.) If the court finds that the accused is incompetent to stand trial, it shall order the accused to be committed to a state hospital for care and treatment to facilitate the speedy restoration of the accused to competence. (Pen.Code, 1370, subd. (a)(1).) Criminal proceedings are suspended while the accused is in the state hospital. The term of commitment to the state hospital is not tied to any sentence, as the accused has not been tried or convicted at the time of commitment. The purpose of such commitments is to restore the competence of the accused, if possible, not to impose punishment. (See People v. Jennings (1983) 143 Cal.App.3d 148, 150, 191 Cal.Rptr. 592 (overruled on another ground in People v. Waterman (1985) 169 Cal.App.3d 977, 215 Cal.Rptr. 534, 85 D.A.R. 2354); accord People v. Deletto (1983) 147 Cal.App.3d 458, 481, 195 Cal.Rptr. 233.)