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In-Depth Coverage Of The Irish And European Markets

Cannabis Impaired Driving

Updated: Dec 1, 2022



Although driving while under the influence of drugs has been against the law since 1961, it was not until 2017 that roadside testing was introduced. Since its introduction, the number of mobile detecting devices increased significantly in 2020, which has also increased detection rates. In 2020 67% of detection cases tested positive for cannabis with over two thousand samples tested, in comparison in 2017 60% of 732 samples tested were positive for cannabis.


The legislation tests for two aspects of cannabis in your system and sets corresponding limits, for Δ9-Tetrahydrocannabinol is 1ng/ml and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol is 5ng/ml, which is low in comparison to other countries. So, what is the difference, in plain English, Δ9-Tetrahydrocannabinol is immediate/recent use and 9-carboxy-Δ9-tetrahydrocannabinol while also recent use, can be detected for far longer, often up to 30 days for a heavy consumer. Studies illustrate that cannabis can sometimes be detected in oral fluid for up to 72 hours. The current advice from the Department of Transportation is to wait 6-24 hours after consumption before driving. In examining the THC detection window De Castro et al found that only 9% of participants tested positive when the cut-off was set at 25ng/ml, compared with 73% of participants when the level was set at5ng/ml and 100% when the level was set at 1ng/ml. A study on Australian drug diving laws found that in Australia, the percentage of THC-positive drivers who are unimpaired is estimated to be 50% based on a 4-hour THC-detection window, If the detection window is 24 hours, that percentage rises to 90%. If these estimates are correct the justice of Ireland's drug driving laws must be called into question.


While we would all agree no one should drive while impaired, there is a difference between the Irish approach to testing for the presence of cannabis and impairment from cannabis. Studies have shown that in comparison to alcohol, the presence of THC is not a good indicator of impairment. The prosecution of cannabis-presence driving offences (in the absence of any behavioural evidence of impairment) is ultimately based on the assumption that there is a tight causal relationship between positive toxicology for cannabis and impairment.


Dr Fabian Pitter Steinmetz a Toxicologist suggests an alternative approach by utilising staggard detection limits. He proposes -3ng/ml would be defined as “sober”, 3-10ng/ml would be under the influence and should be accompanied by an impairment test, and 10+ng/ml automatic impairment.


The majority of the above research is based on the Drager 5000 testing system. Today 1st December, the Medical Bureau of Road Safety announced a new testing system. Using the Securetec® Drugwipe 6s, Garda can now test for the presence of Amphetamine and Methamphetamine for the first time. The test works the same as an antigen test and takes a sample of oral fluid. Assistant Commissioner Paula Hilman said "Today also marks the introduction of a new piece of equipment which will increase our capability to test drivers for the presence of illegal drugs. The DrugWipe 6S is now in use by Gardaí and the streamlined testing process will assist us in our goals of bringing offenders before the courts and making our roads a safer place."


In examining different testing devices, Luit et al found that the DrugWipe® 6S

performed better for THC and amphetamines detection than other devices, with an 81% detection. Despite this, it was also found that 15% of positive THC cases are missed by the device. Therefore, the author of the study found that the device seems to be "insufficiently sensitive for THC detection."


So, what happens if you test positive at a roadside test? A positive roadside oral fluid test will permit you to be brought to the Guarda Station where a blood sample will be collected and sent for analysis. Two samples will be taken, one sent for analysis and one offered to the person who may seek to have their own analysis carried out. If convicted in court for drug driving you will be disqualified from driving, the length of time of disqualification is left to the judge to decide although minimum periods are set out in legislation. There is also a possibility of a fine of up to €5,000 or 6 months imprisonment. No proof of actual impairment is required.


*Those in receipt of medicinal cannabis can avail of a medical exemption certificate from their prescribing doctor.

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