Presumption of possession and knowledge of controlled drugs
18.—(1)  Any person who is proved to have had in his possession or custody or under his control —
(a)anything containing a controlled drug;
(b)the keys of anything containing a controlled drug;
(c)the keys of any place or premises or any part thereof in which a controlled drug is found; or
(d)a document of title relating to a controlled drug or any other document intended for the delivery of a controlled drug,
shall, until the contrary is proved, be presumed to have had that drug in his possession.
(2)  Any person who is proved or presumed to have had a controlled drug in his possession shall, until the contrary is proved, be presumed to have known the nature of that drug.
(3)  The presumptions provided for in this section shall not be rebutted by proof that the accused never had physical possession of the controlled drug.
(4)  Where one of 2 or more persons with the knowledge and consent of the rest has any controlled drug in his possession, it shall be deemed to be in the possession of each and all of them.