Can a defendant assert attorney-client privilege at a hearing?

In People v. Mickle, supra, 54 Cal.3d at pages 181-185, 284 Cal.Rptr. 511, 814 P.2d 290, a competency hearing was held in which a different attorney represented the defendant than in the underlying criminal action. The attorney in the criminal action was called as a defense witness, but stated he could not answer certain questions "unless defendant personally waived the attorney-client privilege and 'possibly the doctor-patient privilege.' " (Id. at p. 181, 284 Cal.Rptr. 511, 814 P.2d 290.) Defendant refused to waive the privilege, and the evidence from defense counsel was not presented. Relying on People v. Samuel, supra, 29 Cal.3d 489, 174 Cal.Rptr. 684, 629 P.2d 485, the defendant argued "that the court erred in presuming him competent to assert the attorney-client privilege over [the competency hearing attorney's] objection." (People v. Mickle, supra, 54 Cal.3d at p. 182, 284 Cal.Rptr. 511, 814 P.2d 290.)