Can a psychiatrist examine a defendant's mental state to determine his competency to stand trial?

Similarly, in United States v. Driscoll, 399 F.2d 135 (2d Cir.1968), a court appointed psychiatrist examined the defendant to determine his competency to stand trial. Testimony based on the examination was introduced at trial to rebut an insanity defense. The court held that the defendant was entitled to notice that the psychiatric examination could be used to establish sanity as well as competency, in part so he could consult with counsel in order to fully and intelligently respond to questions. Id. at 138.