(4)Where any person subject to naval law is being tried on a charge of desertion, improperly leaving his ship, or absence without leave and such person has surrendered himself into custody of or has been apprehended by any person subject to naval law or by a person subject to the law relating to the Government of the regular Army or the Air Force, a certificate purporting to be signed by such person and stating the fact, date and place of such surrender or apprehension shall be evidence of the matters so stated unless the contrary is proved.
