What is the legal test for removing a defendant's attorney from the witness list?

Once a trial court has formally appointed an attorney to represent the defendant, the court cannot later remove the attorney on the grounds of financial ineligibility without the defendant's consent. (Roswall v. Municipal Court (1979) 89 Cal.App.3d 467, 475.) "At that point the court's sole remedy for enforcing a financially able defendant's burden of paying the cost of counsel [would] be a hearing into the matter at the conclusion of the criminal proceedings, as provided for in Penal Code section 987.8." (Ibid.)