In any felony or misdemeanor case wherein the judge of the circuit court, from the affidavit of the defendant or any other evidence certifies that the defendant is financially unable to pay his attorney fees, costs, and expenses incident to an appeal, the court to which an appeal is taken shall order the payment of such attorney fees in an amount not less than $300, costs, or necessary expenses of such attorney in an amount deemed reasonable by the court, by the Commonwealth out of the appropriation for criminal charges. If the conviction is upheld on appeal, the attorney fees, costs, and necessary expenses of such attorney paid by the Commonwealth under the provisions of this section may be assessed against the defendant.