An attorney other than a public defender who acts as counsel for a defendant who is financially unable to obtain investigative, expert or other services necessary to an adequate defense in the defendant's case may request them in an ex parte application addressed to the district court where the action is pending. Upon finding, after appropriate inquiry in the ex parte proceeding, that the services are necessary and that the defendant is financially unable to obtain them, the district court shall authorize counsel to obtain the services on behalf of the defendant. The district court may, in the interests of justice, and upon a finding that timely procurement of necessary services could not await prior authorization, ratify such services after they have been obtained. Within the standards and guidelines adopted by the state board of indigents' defense services, the district court shall determine reasonable compensation for the services and approve payment to the organization or person who rendered them upon the filing of a certified claim for compensation supported by a written statement specifying the time expended, services rendered, expenses incurred on behalf of the defendant, and the compensation received in the same case or for the same services from any other source. Payment shall be made in the manner provided in, and amendments thereto.