In any case in which an attorney from a public defender office represents an indigent person charged with an offense and such person is convicted, the sum that would have been allowed a court-appointed attorney as compensation and as reasonable expenses shall be taxed against the person defended as a part of the costs of the prosecution, and, if collected, shall be paid to the Commonwealth or, if payment was made to the Commonwealth by a locality for defense of a local ordinance violation, to the appropriate county, city or town. An abstract of such costs shall be docketed in the judgment lien docket and execution book of the court.