"We’re going to need scientifically sound, legally defensible tests for impaired driving caused by pot use."

If we are going to need such a test, then we have long needed such a test. A reminder that we lack a roadside screening device and legally defined blood concentration thresholds for a medicine cabinet full of legal and impairing substances, including OTC medications, cold remedies, tranquilizers, sedatives, sleep-aids, painkillers, anti-depressants and Marinol, the legal, synthetic THC pill.