Doubts Cast Over Accuracy Of Mobile Drug Testing
The accuracy of saliva drug tests have been questioned by an Australian study.
The mobile drug tests (MDT) are used to detect Tetrahydrocannabinol (THC), which is psychoactive element of cannabis used by police in Australia, including in NSW and Victoria.
However, a new study by the Lambert Initiative for Cannabinoid Therapeutics at the University of Sydney has raised serious questions about the reliability of the tests.
Researchers tested the efficiency of the two current devices used by authorities, Securetec DrugWipe and the Draeger DrugTest 5000, on 14 participants.
Police around the country can request a driver submit to a MDT if they believe a driver is under the influence of drugs, and it is a criminal offence to refuse.
The participants were given vaporised placebo cannabis, THC-dominant cannabis, or cannabis containing equivalent concentrations of THC and the non-intoxicating cannabinoid CBD (cannabidiol), and then tested at four different times.
They also used driving simulators to test their driving performances after being given the different cannabis forms.
Both MDT devices, which register a 'positive' reading when a certain defined amount of THC is detected, were used to test each participant. A third sample was also taken and tested using laboratory mass spectrometer.
“What we found was that these test results often came back positive when they should have been negative, or conversely that they came back negative when they should have actually been positive,” said lead researcher, Thomas Arkell.
As a drug driving charge can have life-changing effects on a person's life, the "reliability and accuracy" of these tests needs be addressed, Arkell said.
In a statement, NSW Police defended their use of the kits.
"NSW Police Force continues to deliver mobile drug testing, utilising current technology," a spokesperson told 10 daily in a statement.
"Last year we charged almost 19,000 people who put themselves, their passengers and other road users at great risk. Mobile drug testing continues to rollout throughout the New South Wales road network, with a potential 200,000 tests by July 2020”.
Victoria Police said it was "confident that the current roadside drug testing program is effective, as it involves a series of tests to confirm the presence of drugs."
"The purpose of a preliminary oral fluid test is to only detect the presence of drugs. This is not used as evidence in court matters," a spokesperson said.
"Victoria Police is continually exploring both new technology and approaches to better enhance how drug testing is conducted."
The authors of the study claim the widespread implementation of MDT is because of the success by random breath testing.
In 2016, 10,000 cannabis users in NSW were prosecuted for drug driving. By 2020, NSW Police plan to test 200,000 people a year around the state.
But while there is a clear link between alcohol intake, blood alcohol content in a breathalyser and the intoxication effects on a person, the same does not apply to THC.
The levels of THC found in saliva does not accurately reflect a person's cannabis intake or level of intoxication, and the testing devices were not designed to measure driver impairment, said McGregor.
"We should instead be focusing on developing novel methods for detecting drivers who are actually impaired by cannabis," McGregor said.
The study found that participants who tested positive to THC in their saliva actually had no driving impairment and the amount of THC in their system was "negligible".
THC capsules or suppositories leave no trace of THC in the oral cavity, meaning a saliva test would not register the presence of the drug in a person's system, despite being heavily intoxicated.
This can also happen to those who use vaporised cannabis, said McGregor, which would give a negative saliva sample but leave a person too impaired to drive.