Citation: Police v Keith Stewart Mouat [2014] NSWLC 27
Court: NSW Local Court
Date: 22 December 2014
Judge: Heilpern LCM
Background
The defendant was a motorcycle rider who was involved in two separate traffic collisions. Following the incidents, blood analysis revealed the presence of various drugs in his system, including methadone, benzodiazepines (diazepam and nitrazepam), and THC (the active compound in cannabis). He was charged with two counts of driving under the influence of drugs under s 112(2) of the Road Transport Act 2013 (NSW).
The sole issue at hearing was whether the defendant was "under the influence" of the named drugs at the time of each collision. The prosecution relied primarily on expert pharmacological evidence. The defence called its own expert, whose conclusions differed substantially from those of the prosecution's expert.
The defendant's history was relevant throughout: he was a long-term user of methadone and benzodiazepines, taking them in therapeutic doses as part of an established regime. He also disclosed to police, about a week after the first incident, that he had swallowed cannabis he had on him after the first collision and before police arrived at the scene.
Legal Issues
- What does "under the influence" mean for the purposes of s 112(2) of the Road Transport Act 2013 (NSW), given the term is not defined in the legislation?
- Was the prosecution's expert evidence sufficient to prove beyond reasonable doubt that the defendant's ability to ride a motorcycle was impaired by the drugs named in the charge at the time of each incident?
- Where two experts gave conflicting opinions, which evidence should the court prefer and why?
- Whether the charge was limited to proving the influence of the specific drugs named in the court attendance notice.
Decision
The meaning of "under the influence": The Magistrate confirmed that "under the influence" is not defined by the legislation and requires a factual assessment of whether the drug in question actually disturbed the person's capacity to function. Drawing on Mair v Railway Passengers Assurance Co and Sagacious Legal, Heilpern LCM held that the quantity consumed is not determinative. What matters is whether the drug negatively influenced the defendant's ability at the relevant time.
The first charge: The prosecution called John Farrar, a consultant forensic pharmacologist employed by NSW Police, who concluded that the combination of methadone and benzodiazepines impaired the defendant's ability to ride a motorcycle. The Magistrate rejected this evidence. The studies underpinning Farrar's conclusions were epidemiological in nature, drawing correlations across large groups of drivers rather than testing individual impairment. The court found it logically impermissible to apply a population-level statistical risk to a specific individual to establish guilt beyond reasonable doubt. The Magistrate also noted that Farrar's report omitted contradictory findings contained within the very studies he cited, including research acknowledging tolerance effects in chronic users. These omissions, and inconsistencies revealed in cross-examination, significantly undermined his credibility.
The second charge: The second incident involved elevated THC levels detected in blood taken approximately 125 minutes after the collision. The defendant's explanation was that he had consumed raw cannabis after the crash. Farrar rejected this explanation on the basis that consuming raw cannabis plant material could not produce the detected THC concentration. The defence expert, Dr Weatherby, disagreed, pointing to the potency of hydroponically grown cannabis and opining that post-accident consumption was a plausible explanation for the blood reading. The Magistrate preferred Dr Weatherby's evidence and found that the defendant's explanation was a reasonable one consistent with innocence.
Scope of the charge: The Magistrate accepted the defence submission that the prosecution was limited to proving influence caused by the specific drugs named in the court attendance notice. Cannabis was therefore not available as a basis for the first charge.
Orders Made
• The second charge is dismissed.
Key Takeaways
- The Local Court confirmed that "under the influence" under s 112(2) of the Road Transport Act 2013 (NSW) requires proof that a drug actually disturbed the defendant's capacity to function at the relevant time, not merely that they had consumed a quantity of the substance.
- Epidemiological evidence demonstrating a statistical association between drug concentrations and crash risk across populations is insufficient, on its own, to prove beyond reasonable doubt that a particular individual was impaired at a particular time.
- Where a prosecution expert's report omits contradictory findings contained within the studies it cites, particularly on an issue as central as tolerance in chronic users, that omission can critically undermine the weight a court gives to the opinion.
- Conflicting expert evidence requires the court to evaluate the reasoning and methodology behind each opinion, not simply the seniority or institutional affiliation of the witness. In this case, the defence expert's evidence was preferred on both contested issues.
- A charge under s 112(2) is confined to proving impairment caused by the drugs specifically named in the court attendance notice, and the prosecution cannot rely on other substances not identified in the charge.
Legislation and Cases Referenced
Legislation:
- Road Transport Act 2013 (NSW), s 112(2)
Cases:
- Mair v Railway Passengers Assurance Co (1877) 37 LT 356
- Sagacious Legal Pty Ltd v Westfarmers General Insurance (No 4) [2010] FCA
- Vakauta v Kelly (1989) 167 CLR 568