In what circumstances can a defendant bring a motion for a new trial based on incompetence?

In People v. Mendez (2008) 161 Cal.App.4th 1362 (Mendez ), at the defendant's sentencing hearing, defense counsel indicated the defendant wished to make a new trial motion based on counsel's incompetence. (Id. at p. 1365.) When asked what counsel did that was incompetent, the defendant stated eight witnesses had not been called, and two of them stated the defendant did not take part in the fight on which the charges were based. (Id. at p. 1366.) The trial court appointed new counsel for the sole purpose of investigating whether there were grounds for a new trial motion based on the incompetence of trial counsel. Newly appointed counsel reported his conclusion that there were no grounds for a new trial motion, although there might be an issue to be addressed on appeal. The trial court assigned the defense back to defendant's trial counsel. (Id. at p. 1368.)