It’s in development:
WSU chemistry professor Herbert Hill says that the team is using ion-mobility spectrometry – the same tech used by airport security and custom agents to detect drugs and explosives – and repurposing it for the new device. Unlike an alcohol breathalyzer, the WSU solution won’t determine how stoned a driver is, but instead just detect the presence of THC. After that, police would follow up with a blood test to be used as evidence in court, similar to an alcohol DUI.
David Knowles provides context:
While driving while stoned is against the law in all four states—Washington, Colorado, Alaska, and Oregon—where marijuana has been made legal for recreational use, as well in those where the drug has been given the green light for medical use, police have had to rely on blood tests and traditional standardized field sobriety tests such as walking a straight line. A 2012 studyfound that just 30 percent of those under the influence of THC failed the standard sobriety tests, and the results of blood tests can take up to twenty-four hours.
Samantha Murphy Kelly notes that this “isn’t the first time a product intended to keep marijuana-influenced drivers off the road has introduced”:
Earlier this month, a breathalyzer called Cannabix, which also detects THC in one’s system, was revealed at the National Marijuana Business Conference in Las Vegas. Cannabix is slated to roll out first to law enforcement and businesses, then to consumers; it is scheduled to hit the market next year.