What is the onus on the prosecution to prove each ingredient of a drug beyond a reasonable doubt?

It seems evident that O’Halloran, J.A., in Rex v. Hess, supra, held that the onus rested upon the prosecution throughout to prove each ingredient of the offence beyond a reasonable doubt. In that case the evidence established that the accused had the substance in his hand and that the substance was a drug. No evidence was tendered by or on behalf of the accused. The verdict was quashed because the crown had failed to prove beyond a reasonable doubt that the accused knew the substance to be a drug and that the accused had exercised the necessary measure of control. There could have been no such failure by the prosecution in the absence of a corresponding onus.