Building a Weed Breathalyzer Requires the Best Study Ever

In states such as Washington and Colorado, the legalization of recreational marijuana use has brought a shadow market into the open. If you’re into this sort of thing, it’s probably made you a lot less paranoid. But as more people legally smoke up, state and local law enforcement face a buzzkill: There’s no quick way to know if a driver is stoned.

That’s partly because the science of highs is sketchy. A May study from the AAA Foundation for Traffic Safety concluded that there isn’t a reliable link between impairment and the level of THC, pot’s psychotropic agent, in a driver’s blood. Nonetheless, in Washington, as in many states, the legal limit is based on blood concentration. So officials are looking to a septuagenarian chemist to build a breathalyzer for weed. The chemist’s name, of course, is Herb.