In People v. Marsden (1970) 2 Cal.3d 118, the Supreme Court held that when a defendant seeks to discharge appointed counsel and substitute another attorney, the trial court must give the defendant an opportunity to state his reasons before ruling on the motion. In reaching this conclusion, the court started with the propositions that (1) criminal defendants are entitled to the assistance of court-appointed counsel if they are unable to employ private counsel; (2) the right of a defendant to the assistance of appointed counsel may include the right to have appointed counsel discharged or other counsel substituted, if it is shown that failure to do so would substantially impair or deny the right; (3) the right to such discharge or substitution is not absolute, but obtains only if it is sufficiently shown that the right to the assistance of counsel would be substantially impaired in case the request is not granted; and (4) within these limits there is a field of discretion for the court. (2 Cal.3d at p. 123.) Addressing the proper exercise of the trial court's discretion, the court stated: "A trial judge is unable to intelligently deal with a defendant's request for substitution of attorneys unless he is cognizant of the grounds which prompted the request . . . . Thus, a judge who denies a motion for substitution of attorneys solely on the basis of his courtroom observations, despite a defendant's offer to relate specific instances of misconduct, abuses the exercise of his discretion to determine the competency of the attorney." (2 Cal.3d at pp. 123-124.)