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    New research has cast doubt on the accuracy of roadside saliva tests in drive under influence (DUI) cases.

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      drive under influence

      New Research Casts Doubt on Roadside Saliva Tests for Drive Under Influence (DUI) Cases

      New research has cast doubt on the accuracy of roadside saliva tests in drive under influence (DUI) cases.

      Police throughout the country use saliva-based tests for tetrahydrocannabinol (THC), the active compound in cannabis.

      But researchers from the University of Sydney’s Lambert Initiative found that the levels of THC in a person’s system do not directly correlate to how badly a person is affected by the drug.

      Doubt Over Drive Under Influence of Drug Charges

      The researchers combined the results of 28 independent studies to get their results, looking at the effects of both ingested and inhaled THC.

      They came to the conclusion that the levels of THC were more indicative of impairment in occasional users compared to regular users.

      Some people who had only small amounts of THC in their system showed major impairment, and vice versa.

      Lead author of the study, Danielle McCartney, said that THC has a complex interaction with the human body.

      This can be contrasted to alcohol, which clearly affects a person more based on how much of it is in their system.

      “There are a couple of reasons THC might not directly affect someone, despite being in their system. One of those is that there might be different levels of THC in the blood compared to the brain, where it would have an impairing effect,” Dr McCartney said.

      “Another might be that THC is metabolised into other compounds that are impairing themselves, so they could be having an effect on you also.”

      Drive with Illicit Drug Present a More Appropriate Charge

      All States in Australia make it an offence to have any amount of prohibited drugs in your system while driving. There are two offences that are used in NSW.

      The offence of driving with an illicit drug present only requires the prosecution to prove that a person had some amount of an illicit drug in their system.

      This is a less serious offence than a DUI offence, as the prosecution do not have to prove that a driver was actually under the influence of a drug.

      However, Dr McCartney suggested that approach did not reflect the reality that some people were unaffected by certain levels of THC.

      “One of the major recommendations out of this study is that we really need to develop better methods of identifying cannabis-intoxicated drivers,” she said.

      “There’s a lot of work being done in this space, but combining some form of field sobriety test with tests for these biomarkers I think will be the path that this heads down.”

      This is the approach taken in other countries such as the US when it comes to drive under the influence charges.

      Difficult to Judge Level of Impairment

      Study co-author Thomas Arkell revealed they found that people themselves were poor judges of how impaired they were. Drivers tended to underestimate how affected they were and whether they were able to drive after consuming THC.

      “Individuals are better to wait a minimum length of time – between three and 10 hours depending on the dose and route of administration – following cannabis use before performing safety-sensitive tasks,” Dr Arkell said.

      “Smartphone apps that may help people assess their impairment before driving are currently under development and may also prove useful.”

      DUI v Driving with Illicit Drug Present

      Driving with an illicit drug present is defined under Section 111 of the Road Transport Act 2013 (NSW), the prosecution must prove the following, beyond reasonable doubt, for you to be found guilty:

      1. You were driving a motor vehicle on a road or road related area; and
      2. you had a prescribed illicit drug in your oral fluid, blood or urine

      Importantly, there is no need for Police to prove that your driving was affected in any way by the presence of the illicit drugs. This is a common issue as most drugs stay in a person’s system for days. Some drugs such as cannabis can stay in your system for weeks.

      The following are known as prescribed illicit drugs:

      1. Ecstasy (methylamphetamine)
      2. Speed (3,4-methylenedioxymethylamphetamine)
      3. THC (delta-9-tetrahydrocannabinol)
      4. Cocaine

      The offence of drive under the influence (DUI) is set out under Section 112 of the Road Transport Act 2013 (NSW), the prosecution must prove the following, beyond reasonable doubt, for you to be found guilty of a DUI charge:

      1. You were driving a motor vehicle on a road or road related area; and
      2. At the time you were under the influence of any drug or alcohol.

      For this offence, Police do need to prove you were under the influence of a drug. However, the decision of DPP (NSW) v Kirby [2017] NSWSC 1754 explains that the Crown do not have to prove that your driving was affected by drug or alcohol use.

      Another major difference is that there is no need for the drug to be illicit. Even prescription drugs can cause you to fall afoul of this offence.

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