(a) There is imposed, in addition to all other applicable taxes, a state excise tax upon each use, possession, consumption, storage, or transfer of marijuana or any controlled substance.

(b) The tax imposed by this Code section shall apply regardless of whether the substance exists in solid, liquid, or gaseous form and regardless of the degree of purity of the substance. Each person who uses, possesses, consumes, stores, or transfers a substance identified in this Code section shall be liable for the tax imposed by this Code section.