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

"A trial court may remove defense counsel, even over defendant's objections, 'in order to eliminate potential conflicts, ensure adequate representation, or prevent substantial impairment of court proceedings ....' [Citation.] On appeal, the trial court's removal of counsel is reviewed for abuse of discretion. ' "A court abuses its discretion when it acts unreasonably under the circumstances of the particular case." ' [Citation.] 'Inherent in the question whether a trial court may disqualify a criminal defense attorney over the defendant's objection is the conflict between the defendant's preference to be represented by that attorney and the court's interest in "ensuring that criminal trials are conducted within the ethical standards of the profession and that legal proceedings appear fair to all who observe them." ' " (People v. Richardson (2008) 43 Cal.4th 959, 995-996.)