What is the test for whether a defendant is competent to plead guilty?

"The test for whether a defendant is competent to plead guilty is whether 'mental illness has substantially impaired his or her ability to make a reasoned choice among the alternatives presented and to understand the nature and consequences of the waiver.' " United States v. Lewis, 991 F.2d 524, 527 (9th Cir.1993). "Where the evidence raises a 'bona fide doubt' as to defendant's competence ..., the judge on his own motion must impanel a jury and conduct a sanity hearing...." Pate v. Robinson, 383 U.S. 375, 385 (1966). "There are no particular facts which invariably signal incompetence, but important factors which merit a judge's attention include: irrational behavior, demeanor before the court, and available medical evaluations." U.S. v. Lewis, 991 F.2d 524, 527 (9th Cir.1993).