In particular, lawyers say that oral fluid testing is based on unsettled science.
Clients who were not impaired at the time of testing but who yielded a positive result of a certain concentration of nanograms of THC, the active ingredient in cannabis, could face impairment charges because of that scientific uncertainty, lawyers say.
Annamaria Enenajor, a criminal defence lawyer and partner with Ruby Shiller Enenajor DiGiuseppe Barristers in Toronto, says the oral fluid testing can provide reasonable grounds for law enforcement officials to believe that a person has committed an offence of driving while impaired by cannabis.
“The reliability of the tests isn’t a foregone conclusion in terms of what the test actually shows,” says Enenajor. “Unlike breathalyzer tests for alcohol, there isn’t a consensus in the scientific community about the ability of an oral fluid test to determine present impairment.”
Enenajor says there is a consensus that a breathalyzer reading of 0.08 per cent blood alcohol content is indicative of impairment.
However, when it comes to cannabis, the federal government assumes that a positive oral fluid testing result means that a person has probably consumed cannabis in the recent past but is not necessarily impaired at the time the test is conducted.
“The risk that arises from that [positive result] is that a person can be held liable for driving impaired where they are actually not impaired — essentially a false positive can lead to a false conviction,” says Enenajor. “There is no actus rea for the liability.”
Enenajor says the lack of scientific certainty creates a situation where an unreliable oral fluid test creates the reasonable probable grounds for police to proceed with a blood draw test, which she says is also an unreliable test.
For blood draw tests, guilt is established at a level of five nanograms per millilitre of blood.
“It’s layers of problematic assumptions made about the reliability of evidence,” says Enenajor.
Tamara Ticoll, counsel with Stikeman Elliott LLP in Toronto, who practises employment law, says that, for employers, oral fluid testing is considered less invasive than other testing methods.
“There’s less of an infringement on employee privacy rights,” says Ticoll. “It would be seen as a better practice in the jurisprudence.”
Ticoll says the cheek swab of the oral fluid testing is seen as preferable to urine analysis or especially blood testing in a workplace, which is much more invasive and infrequently used.
“Even with those [who test] positive, employers still need to be mindful of the fact that the technology isn’t showing present impairment,” says Ticoll.
“Even if an oral fluid test may be viewed as more precise, it can have limited value in that it doesn’t show present impairment or an ability to pinpoint when the drug was used.”
Ticoll says that because it remains unclear if the drug use caused impairment or impacted fitness for work, it could be challenged.
Ticoll says she tells employers that while the oral fluid testing is a helpful tool, it should be used as part of a policy that couples the oral fluid testing along with testing where an employer also has reasonable grounds to believe that there may have been impairment and where there are signs that are indicative of impairment.
“You have two fronts to establishing that the person is impaired,” says Ticoll. “I would consider that as a best practice versus using just the oral fluid testing on its own.”
Ticoll says that even though the two-part test could still be challenged, the limitations of the technology will mean that this is a rapidly evolving area that employers will need to stay alert to.
Anne-Marie McElroy of McElroy Law in Ottawa says the whole impaired driving regime is premised on a balance of Charter rights and public safety and that roadside tests are allowed without the right to counsel because there is an assumption that the tests are accurate.
“That allows the police the grounds in order to detain a person, often for hours at a time, in order to have them subjected to further tests,” says McElroy. “To know that these instruments can have false positives or may not be accurate undermines the whole scheme that has been carefully crafted in order to balance these competing interests.”
McElroy adds that the other difficulty from a defence lawyer perspective is a lack of access to the machines that were used for testing or their maintenance records, which makes it difficult to determine their reliability.
“It’s hard to prove that they’re not accurate if we don’t have any way of knowing if they’re accurate or not,” says McElroy.