What is the proper procedure for a defendant to bring a motion for a new trial or plea withdrawal?

[1][2] We publish this opinion for the purpose of clarifying the proper procedure for trial courts to follow in the circumstances presented.² That procedure includes 1) making an adequate inquiry of the defendant and his or her defense counsel, to learn the general basis for the defendant's proposed motion; 2) conducting a Marsden hearing, if the general basis for the motion is the alleged incompetence of defense counsel; 3) relieving defense counsel and appointing a new attorney for the defendant if, and only if, "a failure to replace the appointed attorney would substantially impair the [defendant's] right to assistance of counsel." *875 ( People v. Smith (1993) 6 Cal.4th 684, 696, 25 Cal.Rptr.2d 122, 863 P.2d 192 ( Smith ).) The proper procedure does not include the appointment of "conflict" or "substitute" counsel to investigate or evaluate the defendant's proposed new trial or plea withdrawal motion.

As we noted in Eastman: