Does a defendant have a right to retain counsel of his choice at trial?

A criminal defendant has a Sixth Amendment right to retain counsel of his choice. See Wheat v. United States, 486 U.S. 153, 159 (1988). "Absent ... a compelling purpose, ... it is a violation of the Sixth Amendment to deny a motion to substitute counsel and an error that must be reversed, regardless of whether prejudice results." United States v. D'Amore, 56 F.3d 1202, 1204 (9th Cir.1995). A compelling purpose may exist "when granting the motion would lead to a delay in the proceedings and the Government's interest in the prompt and efficient administration of justice outweighs the defendant's need for new counsel to adequately defend himself." Id. (emphasis added). Thus, "even when the motion is made on the day of trial, the court must make a balancing determination, carefully weighing the resulting inconvenience and delay against the defendant's important constitutional right to counsel of his choice." Id. at 1206.