If the consular officer executing any commission authorized under section 3492 of this title shall be satisfied, upon all the testimony taken, that a foreign document is genuine, he shall certify such document to be genuine under the seal of his office. Such certification shall include a statement that he is not subject to disqualification under the provisions of section 3492 of this title. He shall thereupon transmit, by mail, such foreign documents, together with the record of all testimony taken and the commission which has been executed, to the clerk of the court from which such commission issued, in the manner in which his official dispatches are transmitted to the Government. The clerk receiving any executed commission shall open it and shall make any foreign documents and record of testimony, transmitted with such commission, available for inspection by the parties to the criminal action or proceeding in which such documents are to be used, and said parties shall be furnished copies of such documents free of charge.