38 The trafficking offence created by s.71AA is of a quite different kind. The offence is not "defined to include any of several categories of conduct". On the contrary, it is defined by reference to a single type of conduct, that is, trafficking in a commercial quantity of a drug of dependence. As we have already noted, Parliament quite deliberately sought to establish uniformity of the offence - that is, to standardise the offence - across the range of drugs of dependence, by specifying for each drug that quantity the trafficking of which could be characterised as "truly commercial in nature".
39 In short, the whole structure of the trafficking provisions, and the very precise content of the relevant columns in Schedule 11, leads inevitably to the conclusion that, other things being equal, trafficking in a commercial quantity of drug of dependence A is no more nor less serious than trafficking in a commercial quantity of drug of dependence B.[31]
40 As we said earlier, the measure of seriousness which informs the gradation of trafficking penalties from life imprisonment (for trafficking in a large commercial quantity) down to 15 years' imprisonment (for trafficking in less than a commercial quantity) is the quantity of the drug trafficked, not the harmfulness of the drug in question. Apart from that which qualifies the drug in question for membership of the class "drugs of dependence", the characteristics of the trafficked drug are irrelevant.
41 The corollary of this analysis is that the larger the quantity trafficked, the more serious the offence. Take heroin for example. The commercial quantity is 250g, while the large commercial quantity is 750g. An offence under s.71AA involving the trafficking of (say) 700 grams - that is, several times the commercial quantity, and only slightly less than the large commercial quantity - should be regarded as more serious (other things being equal) than an offence involving the trafficking of 275 grams, that is, only slightly more than the commercial quantity.
42 But the most important conclusion to which this analysis leads is that the harmfulness of the drug is an irrelevant consideration. On the proper construction of the quantity-based trafficking provisions (s.71, s.71AA and s.71AC),[32] there is no scope for the court, in sentencing an offender for an offence created by one of those sections, to consider the (relative) harmfulness of the drug in question. That is, Parliament did not intend judges to undertake that task.
43 This does not, of course, prevent the sentencing court from taking into account evidence as to the harm caused by the particular conduct of which the offender has been convicted. The harm attributable to the conduct in question is as relevant as any other factor peculiar to the offending or the offender. What the legislation precludes, in our view, is the sentencing court bringing to bear any view, about the general tendency of the drug in question to cause harm, whether to users of it or to the community at large.
44 Our analysis has been based on the specification in Schedule 11 of the commercial quantity for each of 149 drugs of dependence and the large commercial quantity for each of 10 drugs of dependence. What of the 88 drugs of dependence listed in the Schedule for which no commercial quantity is specified? The offence of trafficking in one of those drugs will be a contravention of s.71AC whatever the quantity trafficked. Section 71AA has no application to dealings in those drugs.
45 We see no reason to think that Parliament intended any other approach to be taken in sentencing for offences of trafficking in those drugs. Parliament is no more to be taken to have contemplated harm-based sentencing in such a case - that is, where a person is convicted under s.71AC of trafficking in a drug of dependence for which no commercial quantity is specified - than in cases where a commercial quantity has been specified for the drug in question. All the considerations to which we have referred point in the opposite direction. The quantity of the drug trafficked will be a factor to be taken into account in sentencing, but it is not for the sentencing court to attempt any assessment of the harmfulness of the drug in question.
Application to other DPCS offences
46 By parity of reasoning, what we have said in relation to the quantity-based hierarchy of trafficking offences applies equally to the quantity-based hierarchy of offences of cultivation of narcotic plants: ss.72, 72A and 72B[33]. Narcotic plants are a sub-set of drugs of dependence for this purpose. General propositions about the relative harmfulness of one narcotic plant as against another have no place in sentencing for an offence under any of those provisions.
47 There are other offences created by Part 5 of the DPCS Act which are not quantity-based. Possession offences under s.73, for example, are differentiated according to whether the person was (or was not) in possession of the drug for a purpose related to trafficking. Thus, s.71AB provides a maximum custodial penalty of 20 years for the offence of trafficking in a drug of dependence to a child (meaning a person under 18), while s.71B provides for a maximum penalty of not more than 1,000 penalty units or 15 years' imprisonment, or both, for the offence of supplying a drug of dependence to a child (either for the use of that child or for the purposes of supply by that child to another child). Again, s.71A provides for a maximum custodial penalty of 10 years' imprisonment for the offence of possessing a substance, material, document or equipment for use for the purposes of trafficking in a drug of dependence.
48 We say nothing about the approach to sentencing for offences under these latter provisions. Clearly, those provisions do not contain the same legislative "cue", based on the weight of the drug involved,[34] as do the quantity-based provisions under discussion. The adoption of a different legislative approach in those sections does not, however, alter the conclusion we have arrived at in relation to the quantity-based offences.
A practical impossibility
49 As suggested earlier, we think it wholly impracticable - and undesirable - for any sentencing judge to attempt to form views about the (relative) harmfulness of the particular drug of dependence the subject of the trafficking charge. This is so whether or not expert evidence is led. The practical impossibility of the task reinforces our conclusion that Parliament did not intend that it be undertaken.
50 The difficulties involved in a judge assessing the seriousness of trafficking in a particular drug of addiction, based upon the characteristics of the substance involved, are numerous. It is necessary to draw attention to only a few.
51 However experienced they may be, few judges can claim any degree of expertise concerning the social or other costs to the community, or the psychological or physical consequences, of the ingestion of even the most commonly encountered drugs. New substances and combinations of substances - concerning which little, if any, experience exists - appear with regularity.
52 Some substances, such as cannabis, which were widely regarded only a few years ago as not particularly harmful or potentially dangerous to the user, are now viewed with greater concern. In the South Australian case of R v Tideman[35], decided in 1976, Bray CJ described cannabis as having a "comparatively innocuous character". Since that time, there is evidence that the tetrahydrocannabinol content of the material available in the community has increased, and it has been recognized that a range of extremely serious physical and mental consequences can be associated with cannabis-use.[36] In 2006, it might well be concluded - on a careful consideration of the empirical evidence, and the research that has been conducted since 1976 into the characteristics and effects of cannabis, both long and short-term - that cannabis can no longer be described as "comparatively innocuous", even allowing for the comparative judgment involved.[37]
53 Of course, to the individual who experiences a psychotic response on ingesting cannabis, or the victim who is assaulted by a person acting under its influence, [38] any relative classification is entirely irrelevant. Such reactions may be less frequent, and the personal and social damage resultant from the use of the substance may be less severe, than is the case with other drugs, but there is a powerful argument that those who trade for financial advantage in a drug known to be potentially harmful should not be able to mitigate their conduct by arguing that the risks to users of that drug are statistically lower than those associated with other drugs.
54 Four years before the judgment of Bray CJ in Tideman, a differently- constituted Full Court in South Australia said in Beresford[39] -