The reversal of the onus of proof in drug-possession cases is incompatible with the rule of law and is therefore unconstitutional in ALL jurisdictions. If you're a juror in a trial for possession of a prohibited drug, and if you are told that the "law" requires the defendant to prove that the possession was unwitting, it is your civic duty to put the onus of proof back where it belongs (on the prosecution), raise it to the proper standard (beyond reasonable doubt), and hand down a verdict on that basis.

In the "war on drugs", the presumption of innocence is not collateral damage. It is a deliberate target: if other people plant drugs on you (e.g. to avoid being busted themselves), you must prove that your possession of the drugs was unwitting (which you can't). This situation is manifestly incompatible with the rule of law, because the power to convict... is effectively taken from the courts and given to those who are willing to plant evidence. There is no clearer case of a "government of laws" being usurped by a "government of men".

In the few jurisdictions in which a person claiming unwitting possession faces only an "evidential" or "evidentiary" burden of proof... the key question is whether an innocent person would necessarily be able to adduce sufficient evidence... It would seem that the answer is negative, in which case the breach in the rule of law remains.

The purported reversal of the onus of proof, being contrary to the rule of law, is unconstitutional for at least three reasons:

First, the mere existence of a constitution, written or unwritten, presupposes the rule of law and therefore invalidates any legislation or judicial precedent incompatible with the rule of law.

Second, the mere existence of a court presupposes the rule of law and therefore precludes the court from entertaining any proposition incompatible with the rule of law: to compromise the rule of law would be repugnant to the institutional integrity of the court.

Third, the legislative power is limited to the making of law, which by definition must be compatible with the rule of law...

Wherever there is an overriding prohibition on cruel or unusual or degrading punishment, there is a fourth reason, namely that the reversal of the onus of proof foreseeably leads to punishment of innocent people, such punishment being cruel or unusual or degrading by reason of their innocence...

Indeed, reversing the onus of proof protects the bosses of the drug trade: if the bosses arrange for the drugs to be in the "possession" of some unsuspecting person, and if that person is caught, that person takes the rap and the investigation never reaches the bosses...

Full text: The universally unconstitutional war on drugs.