False positives in drug-driver tests could be hurdle
Surmount that issue by doing test twice, says MP Nick Smith
Drivers testing positive for drugs they have not taken could prove problematic for any plans to adopt roadside drug driving testing in New Zealand.
But experts and advocates say the policy is still worth pursuing to help save lives on the roads.
This week, Associate Transport Minister Julie Anne Genter and Police Minister Stuart Nash called for public consultation on the issue of drug-driver testing.
Ministry of Transport data shows drugs were the reason for 21 per cent of New Zealand fatal crashes in 2017 — ahead of alcohol at 18 per cent.
The UK, Canada and Australia all have roadside drug-driving tests. Despite this, implementing them here is not as simple as it may seem.
Genter said as much on Wednesday: “Unlike with alcohol testing, drug testing comes with some unique challenges, which is why we want expert and public input into the design process.”
Unlike alcohol breath tests, drug tests can only detect the presence of drugs or medication. They cannot test if a driver is impaired.
And this is by no means the only problem. According to a discussion document prepared by the Ministry of Transport on enhanced drugimpaired driver testing, the issue of false positives could be a concern.
“The technology of oral fluid drug detection devices is improving, however, there is a residual risk of screening devices producing false positives,” the document said.
A 2017 study in Canada found that in 7 per cent of cases, where subjects had not used any of the substances, tests produced a false positive.
To put that in perspective in a New Zealand context, in
2017/18 police carried out 1.7 million breath alcohol tests.
If 7 per cent had produced false positives, just under
12,000 people would have been told incorrectly they were over the limit.
Genter said drug testing was evolving.
“That’s one of the reasons we have taken a careful and robust approach and why we’re going out to consult now, instead of just knee-jerk rolling them out.
“We want to make sure that we’re going to get a fair outcome and that it’s going to reduce impaired driving.”
The issue of false positives in drug testing has come up in Australia too. In 2015, a police officer told a motorist, Steve Hunt, he had tested positive for methamphetamine despite Hunt never having taken it in his life. Hunt’s lawyers demanded the sample be retested, according to the Sydney Morning Herald. When the test came back, it got a negative result and the court case was dismissed.
And this was not an isolated incident. But National MP Nick Smith said there was a simple way to mitigate the issue — do the test twice.
He has been critical of the Government for taking too long to get the test up and running.
“All these arguments were had when the Government introduced random alcohol roadside testing.”
He said the change in social attitude, driven by random roadside alcohol testing, had seen fatalities drop dramatically. There was the potential to reduce the number of deaths from drug-driving.
Helen Poulsen, a forensic toxicologist with the Institute of Environmental Science and Research, said there was no real way to mitigate against false positives. And there was
another issue: “All those oral fluid tests do is look for the possible presence of a drug — usually cannabis, meth or MDMA. Just because someone has some drug in their oral fluid, or even their blood, it doesn’t mean that they are impaired by that drug.”
However, she said testing would help change attitudes around people taking drugs and driving.
“If roadside testing and having that presence of the police with the big booze bus, with drug-testing on the side — if that deters some people and prevents more accidents, it can only be good.”
Last week the Government was urged to give police more support on driver drug testing. The call was made by Logan Porteous who lost his parents Ian, 80, and Rosalie,
76, in a crash that killed seven in Taranaki last year. Rosalie’s sister, Ora Keene, 84, and her friend Brenda Williams, 79, also died; as did the driver of the other car who had smoked synthetic drugs before the crash, Jeremy Thompson, 28, his newborn daughter Shady, and 8-yearold step-daughter Nivek Madams.
After the Coroner’s inquest, Logan said: “We will, as a family, fight for this in the name of the innocent people who were killed in this accident, as a result of a driver under the influence of drugs.”
Porteous noted the Government had quickly changed gun laws after the mosque shootings.
“So it can be done again, it’s up to the politicians.”