What is the test for a defendant's right to retain counsel of his own choosing?

The right to the effective assistance of counsel "encompasses the right to retain counsel of one's own choosing. [Citations.]" (People v. Holland (1978) 23 Cal.3d 77, 86, 151 Cal.Rptr. 625, 588 P.2d 765.) Underlying this right is the premise that "chosen representation is the preferred representation. Defendant's confidence in his lawyer is vital to his defense. His right to decide for himself who best can conduct the case must be respected wherever feasible." (Maxwell v. Superior Court (1982) 30 Cal.3d 606, 615, fn. omitted, 180 Cal.Rptr. 177, 639 P.2d 248.)

Protection of this right furthers other values important to our criminal justice system. The right to employ counsel of one's own choosing "is based on a value additional to that insuring reliability of the guilt-determining process. Here we are concerned not only with the state's duty to insure 'fairness' in the trial, but also with the state's duty to refrain from unreasonable interference with the individual's desire to defend himself in whatever manner he deems best, using every legitimate resource at his command." [37 Cal.3d 790] (People v. Crovedi (1966) 65 Cal.2d 199, 206, 53 Cal.Rptr. 284, 417 P.2d 868.)