In all Australian jurisdictions, the unauthorised possession of illegal drugs is an offence. But what does this mean? “Possession” of illegal drugs under the common law involves physical control over the drugs (actively excluding others from them) and intent to exercise dominion over them. The law will not care that possession was only temporary. However, it will care if the possession was accidental or the defendant was unaware of the presence of the drugs.
Temporary (or “Doomed”) Possession
In R v Boyce (1976) 15 SASR 40, the defendant was arrested at an airport with a suitcase containing 4.3kg of Indian hemp (cannabis). He argued that, although he exercised physical control over the drugs, his collection of them had been supervised by police, who would never have allowed him to leave the airport with them. His possession was “doomed” from the start, and thus he “had no real exclusive physical control over the case and its contents”.
Rejecting that line of argument, Bray CJ stated: “[t]he argument confuses the existence of control with the permanence of control”. The defendant in R v Boyce was held to have had de facto possession of the illegal drugs, if only for a short period of time.
In R v Thomas (1981) 6 A Crim R 66, possession over illegal drugs was temporary due to an exercise of control by the defendant. The defendant became aware of cannabis that had been left at his residence. During a police raid, he threw the cannabis over his veranda so as not to be caught with it. Lucas SPJ found that, in doing so, the defendant was asserting a right to control the cannabis by disposing of it (an act of possession). In the later case of He Kaw Teh v The Queen (1985) 157 CLR 523, Gibbs J commented that (somewhat amusingly) a person who innocently discovered drugs on the ground and was in the process of taking them to police would also be considered a temporary possessor. We can only hope the police would exercise restraint in pursuing such a person.
Deemed and Unknowing Possession
What if the defendant in R v Thomas had left the cannabis untouched, instead of attempting to pass it “out of human control”? In R v Solway  2 Qd R 75, the defendant was questioned by police over a bag of cannabis found in his bathroom cupboard. He told police that the bag had been left there by somebody at a party, and that he hadn’t disposed of it yet because it had “slipped [his] mind”. At first instance he was held to possess the drugs, but on appeal, Demack J (Campbell CJ and Connolly J agreeing) stated that “mere knowledge of [the drug’s] existence coupled with a future intention to exercise control is not enough”. A person must “not only know of [a drug’s] existence, but he must have laid some claim to it, or exercised some control over it”. Despite this, a person may still be “deemed” to possess illegal drugs found on premises occupied by them (and if exclusive possession cannot be proved in the case of multiple occupiers, each occupier may be “deemed” in possession: R v Fox  2 Qd R 402), although the issue of awareness may come into play here.
A person who carries a bag containing drugs will not “possess” those drugs if he or she is unaware of their existence (see He Kaw Teh v The Queen, Gibbs CJ at 539). Presumably, if drugs are unknowingly present in a home, that also will not constitute possession by the occupiers.
The onus of proving a lack of knowledge of the drugs (or that a substance was not an illegal drug) is on the defendant, not the prosecution. In Tabe v The Queen  HCA 59, the High Court held that the concept of possession did not involve, as an element, knowledge that the thing possessed was a “dangerous drug”. (This reverse burden of proof was further examined in Momcilovic v The Queen  HCA 34.)
The obvious answer would be to not possess illegal drugs. However, where one has unknowingly come into the possession of such drugs, it is interesting to see how actions one might expect to be innocent (eg disposing of them) could instead be read in the opposite light.
Possession of illegal drugs is discussed in The Laws of Australia Subtitle 10.6 “Drug Offences”.
For more information about The Laws of Australia, click here.