A Canberra woman has been cleared of drug driving after she convinced a court she had inadvertently inhaled the drug ice at a party.
Police caught Karlene Helmling in a roadside drug test on Anzac Day in 2019.
But she maintained she had never taken ice, or methylamphetamine, and was stunned to deliver a positive result.
The court heard she went to a party the day before to pick up a friend and, while waiting, was in a room with people smoking the drug.
She said her throat began to burn and she went outside.
Now, three-and-a-half years later, the charge has been dismissed, partly because the ACT Magistrates Court found authorities could not demonstrate that the quantity of the drug in Ms Helmling's system was sufficient for her to threaten road safety.
Magistrate Glenn Theakston accepted her evidence that she had not knowingly consumed methylamphetamine and was unaware of why it was in her oral fluid.
"While the evidence does not allow me to make the positive finding that the defendant's positive result for methylamphetamine was caused by her inadvertant exposure the day before to smoke containing methylamphetamine, that cannot be discounted and remains open on the evidence, he said.
Passive drug use 'happens regularly'
The case has reignited a debate about why Australian police test only for the presence of drugs in roadside oral swab tests, rather than look at drug levels.
David Heilpern, the dean of law at Southern Cross University, said Ms Helmling's situation was relatively common.
"They test for presence, and that presence bares no relationship to intoxication whatsoever," Mr Heilpern said.
He said he saw similar cases regularly when he worked as a New South Wales magistrate.
"People who had been to parties where there are amphetamines would then test positive to amphetamines either the same day or the next day," he said.
"With THC [a compound in cannabis], people who had been in a room or a caravan [with others] who were smoking non-stop, they would test positive the next day.
"Because the samples are so small, the passive consumption is not only possible, it happens fairly regularly and people get caught by these provisions."
Ms Helmling's lawyer, Steven Whybrow, said the consequences could be significant.
"The effect is that somebody who is a tradie and had a couple of joints on a Friday night then on Monday morning tests positive to cannabis, they'll lose their licence, and then possibly their employment and their means of paying off their mortgage and their loans, etcetera," Mr Whybrow said.
Inconsistent lab testing under debate
A police mistake also affected Ms Helmling's case: officers did not inform her she was entitled to have a so-called "B" sample analysed by an independent laboratory.
This led to a debate in court about how ACT authorities determined whether a drug was present in a person's blood.
The ACT regards 4 nanograms per millilitre of blood as a positive test, while the Australian standard is 25 nanograms.
"The analyst accepted that if her B sample had been sent to a laboratory that did apply the Australian standard, it's possible that it would have come back as negative," Mr Whybrow said.
"In which case there wouldn't have been a prosecution.
"We called expert evidence that anything under 25 [nanograms] is not indicative of impairment, is not indicative of any effect, it's not indicative of recent use and it could be more consistent with inadvertent use, such as passive smoking."
Mr Heilpern said many people caught by the laws were not impaired and, if they were, would be charged with other driving offences.
"We have these laws that are really not about road safety — they are really about a prohibition," he said.
"They are really about a backdoor method of trying to stop people using drugs."
However, Mr Whybrow said tough laws should apply for drivers impaired by drugs.
"There's no question the legislation needs to be there, and it needs to be an offence to drive [drug-affected], as it is an offence to drive under the influence of alcohol," he said.
In a statement, the ACT government said it had no plans to change drug-testing arrangements, though it was monitoring national and international research in the area.
