(a) Except as provided in Article 5 of this chapter, whenever it appears to the presiding judge of the superior court that a defendant indicted for a capital felony is indigent and unable to pay an attorney for his defense, it shall be the duty of the court to appoint one or more attorneys for the defendant; and each of the attorneys so appointed shall receive a reasonable sum in compensation for his services in the superior court, as determined in the discretion of the court, plus such sums as have been actually and prudently incurred in the necessary preparation and investigation of the case.

(b) Upon completion of all services by an attorney appointed under this Code section, the attorney shall submit to the court an affidavit containing an accurate statement of all services rendered and expenses incurred. The court, upon examination of the affidavit and approval thereof, shall discharge the attorney and shall enter an order directing the county treasurer of the county in which the defendant was indicted to pay to the attorney such amount for compensation and expenses as the court orders.