Drug driving in NSW: what police actually test for, how the Mobile Drug Testing program works, and what happens if you are charged
Drug driving is one of the most commonly charged traffic offences in NSW, and the way it is investigated and prosecuted differs fundamentally from the drink driving framework that most people are more familiar with. There is no drug equivalent of the legal blood alcohol limit. There is no blood drug concentration below which you are automatically in the clear. Under NSW law, the presence of any detectable prescribed illicit drug in your oral fluid or blood while you are driving, attempting to drive, or in control of a vehicle is an offence – regardless of when you last used the drug, how impaired you were, or whether the drug was affecting your driving at all.
This no-threshold approach means that drug driving prosecutions are overwhelmingly won or lost on the question of whether the drug was detected, not on questions of impairment or concentration. Understanding exactly how detection works, what drugs are tested for, and what legal options are available if you receive a positive result is essential for anyone who uses recreational or medicinal substances and also drives.
The offences – what section 111 of the Road Transport Act says
The primary drug driving offence is found at section 111 of the Road Transport Act 2013 (NSW). A person must not drive a motor vehicle, or attempt to put a motor vehicle in motion, or occupy the driving seat and attempt to put the motor vehicle in motion, while a prescribed illicit drug is present in the person’s oral fluid or blood. The prescribed illicit drugs under the legislation are: THC (tetrahydrocannabinol, the active compound in cannabis), MDMA (3,4-methylenedioxymethamphetamine, ecstasy), methylamphetamine (ice, speed), and cocaine. These are the four drugs for which roadside saliva testing is currently conducted in NSW.
The maximum penalty for a first offence of driving with a prescribed illicit drug present is a fine of $2,200 (20 penalty units) and automatic licence disqualification. For a second or subsequent offence, the fine increases to $3,300 (30 penalty units) and the disqualification period increases. In the Local Court, where most drug driving matters are heard, magistrates have discretion in sentencing within the maximum range, and a person who pleads guilty and presents strong mitigation may receive a lesser fine and a shorter disqualification than the maximum.
How Mobile Drug Testing works in NSW
NSW Police operate Mobile Drug Testing (MDT) through a network of random testing stations similar in concept to Random Breath Testing operations. At an MDT station, drivers are directed to stop. An officer asks the driver to sit with their mouth open while a swab is placed under the tongue and held there to collect saliva. The swab is then tested on a device that can produce a preliminary result within minutes.
If the preliminary test shows a positive result for one of the prescribed illicit drugs, the driver is required to wait while a second saliva sample is taken and tested. If the second sample also returns a positive, the driver is taken to a police vehicle or facility where a blood sample is collected by a trained sample taker. The blood sample is analysed by NSW Health Pathology forensic laboratory. The blood analysis result is the primary evidence used in court. A positive blood result for a prescribed illicit drug will typically result in a formal charge.
Cannabis and the detection window problem
Cannabis creates a distinctive drug driving problem because THC can remain detectable in saliva or blood for a period that can substantially exceed any period of impairment. Oral fluid tests can detect THC in some people for up to twenty-four hours after use. Blood tests may detect THC for longer periods in heavy or chronic users. This means that a person who consumed cannabis the previous evening, slept, and genuinely experienced no impairment whatsoever when they drove the following morning can still return a positive test and face a drug driving charge.
The NSW drug driving offence does not require impairment. It does not require a concentration above any threshold. It simply requires presence of the drug in the oral fluid or blood. This approach is confirmed in the legislation and has been upheld in numerous court decisions. Courts have consistently rejected the argument that a lack of impairment provides a defence to the charge. The only question in most contested matters is whether the drug was actually present in the sample as alleged.
Medicinal cannabis and the current legal gap
The rise of lawfully prescribed medicinal cannabis in Australia has created a significant legal problem for NSW drug driving law. A person who is lawfully prescribed medicinal cannabis, who takes their medication exactly as directed, and who is entirely unimpaired when they drive may still commit the drug driving offence if THC is present in their oral fluid or blood. NSW law currently provides no defence based on lawful medicinal prescription for cannabis, unlike the position that applies to other prescription medications that may cause impairment.
This issue has been raised repeatedly in legal and policy forums, including by the NSW Government’s own drug driving review processes. It remains a live policy debate. For the person currently facing a drug driving charge based on medicinal cannabis use, the absence of a statutory defence means that a well-prepared sentencing submission addressing the medicinal nature of the use and any related hardship from disqualification may be the most practically useful legal avenue.
Challenging a drug driving charge – what can actually be argued
The limited defences available in drug driving matters mean that genuine contests are less common than in some other offence categories, but several arguments can be explored. The reliability of the oral fluid test and the chain of custody of the blood sample are both areas that can be examined. A positive oral fluid test that was not properly stored or handled before laboratory analysis, a blood sample where chain of custody is questionable, or a laboratory certificate that contains errors or omissions can all potentially be challenged. The instructions given to the testing officer and whether the testing process was conducted strictly in accordance with the legislative requirements may also be relevant.
Licence disqualification and the impact on daily life
The most practically significant consequence of a drug driving conviction for most people is not the fine but the mandatory licence disqualification. A first offence typically attracts a minimum three-month disqualification, with automatic disqualification applicable from the date of conviction. For people whose employment, care responsibilities, or daily life depends on being able to drive, a three-month disqualification can have severe practical and financial consequences. Courts have limited power to reduce the disqualification below the minimum prescribed period, but a well-presented hardship submission can sometimes influence the overall approach taken by the magistrate.
Contact Us
At National Criminal Lawyers, we advise on drug driving charges across NSW, including matters involving medicinal cannabis, testing procedure challenges, and hardship submissions on licence disqualification. If you have been charged, obtaining advice before your first court date is worthwhile even in a matter that appears straightforward. Call us at 1800 CRIM LAW for a free consultation. Help us help you understand your situation and get you the best outcome possible.
