Prosecutions in relation to illicit drugs in Western Australia are usually brought pursuant to the offences found in sections 6 and 7 of the Misuse of Drugs Act 1981 (WA).
The majority of these prosecutions relate to well known drugs including: Cocaine, Cannabis/marijuana, Methylamphetamine, MDA, MDMA and Opium. These (and a great many more) are expressly listed in Schedule I ((to which one refers via the definition of ‘prohibited drug’ in s 3(1) of the Act and the operation of s 4.)) to the Misuse of Drugs Act as a prohibited drug. That makes prosecutions in relation to these drugs a relative straightforward matter. A pharmacist simply gives evidence that the substance in question is the prohibited substance. The Jury is then likely to move on to consider whether the accused knowingly possessed the substance, had an intention to sell or supply it or indeed actually sold it.
There are also categories of prohibited drugs that are not expressly listed in Schedule I to the Misuse of Drugs Act.
The Court of Appeal has recently published a useful decision that talks through the process whereby drugs listed in a Federal legislative instrument are deemed to be prohibited drugs. In Clegg v WA [No 2]  WASCA 30 the Court summarised the situation as follows at :
The status of a substance as a prohibited drug is produced by the interaction of the Drugs Act, the Poisons Act 1964 (WA) and the Standard for the Uniform Scheduling of Medicines and Poisons (SUSMP) made under the Therapeutic Goods Act 1989 (Cth) (TGA). These provisions are to be construed together as part of an overlapping legislative scheme. ((In turn citing Trajkoski v Director of Public Prosecutions  WASCA 119 ; Reid v Director of Public Prosecutions  WASCA 190  and as occurred in Sgarlata v The State of Western Australia  WASCA 215; (2015) 49 WAR 176  – .))
The appeal was concerned with a substance, Alpha-PVP, which at the relevant time was not mentioned in any of the interacting legislation. The prosecution alleged that Alpha-PVP was a “derivative” of a substance that was listed in the Standard for the Uniform Scheduling of Medicines and Poisons (“SUSMP”), namely MDPV.
In their appeal against conviction the accused argued (unsuccessfully) that the prosecution’s expert evidence was insufficient to establish that Alpha-PVP was a derivative of MDPV.
The Court noted, at , the context in which the term ‘derivative’ appears strongly suggests that it is used in the sense that it is employed in the science of chemistry. Where a word or phrase has a technical meaning in relation to a particular expertise, and is used in a context dealing with that expertise, it is to be given that meaning unless the contrary intention appears.
The appellants had sought to place weight on a part of the introduction to the SUSMP in these terms:
It is important to note that a substance is not classed as a derivative on the basis of a single, prescriptive set of criteria. Classification of a substance as a derivative of a scheduled poison relies on a balanced consideration of factors to decide if a substance has a similar nature (e.g. structurally, pharmacologically, toxicologically) to a scheduled poison or is readily converted (either physically or chemically) to a scheduled poison. ((See  and following of the judgment.))
The State’s expert focused almost exclusively on the ‘structurally’ similar nature, without considering pharmacological and toxicological similarity.
The Court set out its preferred construction of the term derivative as used in the SUSMP at  to .
Clegg is a useful case to remember, if only as a guide on how to work through the interacting legislation.