Right now if a Washington policeman suspects a driver is under the influence of drugs, they have to get a warrant to have blood drawn, but the results might not come back for weeks. WSU chemist Herb Hill is leading a team trying to shorten that process, testing a prototype device that uses ion mobility spectrometry as a breath test for THC. All they know so far is that the device works, but there are years of refinement ahead to figure out how different people's bloodstreams process the drug. The presence of THC on the breath doesn't mean that a driver is over the five nanograms-per-milliliter limit for legal impairment set down in Washington and Colorado.
Even the Washington State police say this process will take time, because whatever device they end up using has to "prove highly accurate." That hasn't stopped Colorado police from using other methods: last year the Colorado State Patrol began training Drug Recognition Experts and rolled out a campaign that cautioned, "Drive high, get a DUI." Europe appears to be ahead of us in this department: some countries have had roadside drug testing for years, and England and Wales just started their roadside drug testing at the beginning of the 2015.