Mr. Oakes is compelled by s. 8 to prove he is not guilty of the offence of trafficking. He is thus denied his right to be presumed innocent and subjected to the potential penalty of life imprisonment unless he can rebut the presumption. This is radically and fundamentally inconsistent with the societal values of human dignity and liberty which we espouse, and is directly contrary to the presumption of innocence enshrined in s. 11(d). Let us turn now to s. 1 of the Charter. [para 61] In my view, s. 8 does not survive this rational connection test. . . . possession of a small or negligible quantity of narcotics does not support the inference of trafficking. In other words, it would be irrational to infer that a person had an intent to traffic on the basis of his or her possession of a very small quantity of narcotics. [para 78] --R. v. Oakes  1 SCR 103 Introduction
In 1981 David Edwin Oakes, a 23-year-old construction worker, was approached by police outside a tavern in London, Ontario. They found eight one-gram vials of hashish oil worth $150 and $619.45 in cash on him. He was charged with unlawful possession of a narcotic for the purpose of trafficking, under the then Narcotic Control Act. Under section 8 of that Act, if you were found guilty of possession of a certain amount of an illegal narcotic, you would be convicted of trafficking in that drug, unless you could prove otherwise. This "reverse onus" was a rare and contentious part of the criminal law in Canada which effectively forced an accused person to prove his or her innocence. At the time, conviction for trafficking in the narcotic carried a maximum penalty of life imprisonment.
So began one of the most famous cases in Canadian legal history, R. v. Oakes,  1 SCR 103 [http://canlii.ca/t/1ftv6]. It would set one of the most important legal precedents to do with the application of the Charter of Rights.
Oakes claimed that the drugs in his possession were for purely personal use to relieve his pain from a workplace accident. He said the money was from having recently cashed his worker's compensation cheque.
His lawyer took aim at the constitutionality of the reverse onus when the Charter came into effect the next year. Oakes' position was that the reverse onus in section 8 of the Narcotics Control Act violated the presumption of innocence contained in section 11(d) of the new Charter. Even if the reverse onus did violate the constitutional presumption of innocence...