(a)
(1) It shall not be necessary for the Government of the Virgin Islands to negative any exemption or exception set forth in this chapter in any complaint, information, indictment, or other pleading or in any trial, hearing, or other proceeding under this chapter, and the burden of going forward with the evidence with respect to any such exemption or exception shall be upon the person claiming its benefit.
(2) In the case of a person charged under section 607(a) with the possession of a controlled substance, any libel identifying such substance for purposes of section 503(b)(2) of the Federal Food, Drug, and Cosmetic Act shall be admissible in evidence and shall be prima facie evidence that such substance was obtained pursuant to a valid prescription from a practitioner while acting in the course of his professional practice.
(b) In the absence of proof that a person is the duly authorized holder of an appropriate registration or order form issued under this chapter, he shall be presumed not to be the holder of such registration or form, and the burden of going forward with the evidence with respect to such registration or form shall be upon him.
(c) The burden of going forward with the evidence to establish that a vehicle, vessel, or aircraft used in connection with controlled substance in schedule I was used in accordance with the provisions of this title shall be on the persons engaged in such use.
(d) No civil or criminal liability shall be imposed by virtue of this chapter upon any duly authorized Government officer or employee lawfully engaged in the enforcement of this chapter.