When will a court appoint a new attorney to investigate trial attorney incompetence?

This question of appointment of counsel to investigate trial attorney incompetence ordinarily arises where defendant was represented at trial by appointed counsel. "When, after trial, a defendant asks the trial court to appoint new counsel to prepare and present a motion for new trial on the ground of ineffective assistance of counsel, the court must conduct a hearing to explore the reasons underlying the request. [Citations.] If the claim of inadequacy relates to courtroom events that the trial court observed, the court will generally be able to resolve the new trial motion without appointing new counsel for the defendant. [Citation.] If, on the other hand, the defendant's claim of inadequacy relates to matters that occurred outside the courtroom, and the defendant makes a `colorable claim' of inadequacy of counsel, then the trial court may, in its discretion, appoint new counsel to assist the defendant in moving for a new trial. [Citations.]" (People v. Diaz (1992) 3 Cal.4th 495, 573-574.) We conclude that the same rules should apply in the circumstances of this case where defendant is represented at trial by retained counsel but elects to represent himself at sentencing. We also conclude there was no abuse of discretion.