Okla. Stat. tit. 21, § 1726

A. Any person who may be found in this state with more than one (1) pound of mercury in his possession, and who does not have valid written evidence of his title to such mercury, shall be guilty of a Class D1 felony offense and upon conviction thereof shall be punishable by imprisonment as provided for in subsections B through F of Section 20N of this title, or by a fine not exceeding Five Hundred Dollars ($500.00), or by both such fine and imprisonment. B. It shall be a defense to any charge under this section that the person so charged (1) is a bona fide miner or processor of mercury or (2) that the mercury possessed by such person is, while in his possession, an integral part of a tool, instrument, or device used for a beneficial purpose. In any complaint, information, or indictment brought under this section, it shall not be necessary to negative any exception, excuse, exemption, or defense provided in this section, and the burden of proof of any such exception, excuse, exemption or defense shall be upon the defendant.