drug driving saliva tests may not be accurate

Drug-driving Saliva tests may not be accurate
http://www.stuff.co.nz/4233107a11.html

Scientists are testing the accuracy of saliva tests in detecting drugged drivers, following research showing that the problem is more widespread than drink driving.

Research from Otago University's long-running Christchurch Health and Development study released yesterday showed 25-year-olds more commonly drove while under the influence of cannabis than alcohol.

The Otago University figures supported Environmental Science and Research (ESR) data published by The Press this week which gave the first glimpse of the huge problem of drugged drivers on New Zealand roads.

The results of the Otago study also came as Parliament considered legislation to give police greater powers to test and arrest drugged drivers.

In response to the new figures on the scope of drug driving, ESR scientists have launched a study into how effective a saliva cannabis test is in detecting recently consumed drugs.

It is hoped police will in future be able to use the saliva tests to accurately detect whether someone is still under the influence of cannabis while behind the wheel.

Almost 1000 25-year-olds took part in the Otago University research and were asked how many times in the last four years had they driven either dangerously drunk or soon after after smoking marijuana.

Participants said they had driven while under the influence of cannabis an average of nine times in four years, compared to about three times while drunk.

The lead researcher for the Otago University study, Professor David Fergusson, said he was very surprised by the research results. "We never expected to see that cannabis was going to be a bigger problem than drink-driving but that's what we found."

Fergusson said drink-driving had decreased while cannabis use had increased "dramatically" over the decade or so.

More than 80 per cent of 25-year-olds in the study said they had smoked cannabis, Fergusson said.

Under legislation currently being considered by Parliament, police will put suspected drugged drivers through a roadside test of balance, co-ordination and eye-pupil response tests. If they appear to be affected, they will be ordered to have a blood test.

Critics of the legislation argue blood tests detect cannabis in a person's system long after they have smoked it.

The scientist in charge of an ESR and police project to measure the numbers of dead drivers who had taken drugs disputed the claim.

ESR forensic toxicologist Helen Poulsen said blood tests picked up the presence of cannabis in a person's system from between four hours and 24 hours after they had smoked it.

There were currently some issues with the accuracy of saliva tests, Poulsen said.