Can a defendant withdraw his plea of guilty as a result of an unfulfilled promise from a District Attorney?

Of course, a guilty plea induced by an unfulfilled promise either must be vacated or the promise honored (Santobello v. New York, 404 U.S. 257, 260, 92 S.Ct. 495, 30 L.Ed.2d 427 Supra). The District Attorney concedes that the arraignment prosecutor's promise did induce defendant's plea of guilty. That promise should be treated, in substance, although it was not in that form, that defendant would be permitted to withdraw his plea if a prison sentence were to be imposed. Withdrawal of a plea, however, is not within the power of the prosecutor. That power rests solely in the discretion of the court (CPL 220.60, subd. 4). The prosecutor, without authority, promised that which he could not legally perform and the defendant, therefore, could not, as a matter of law, rely on that promise.