How do they test for driving under the influence of marijuana?

For Marijuana, using blood, breath, or urine tests to determine whether a person is under the influence of THC at the time they were driving is a flawed system, as blood and urine tests are unable to determine whether Marijuana was consumed within the last few hours while breath testing technology does not have the ability to detect Marijuana, as of now. read more

This so-called standard field sobriety test has been shown to catch 88 percent of drivers under the influence of alcohol. But it is nowhere near as good at spotting a stoned driver. In a 2012 study published in the journal Psychopharmacology, only 30 percent of people under the influence of THC, the active ingredient in marijuana, failed the field test. read more

Laws defining what it means to be “under the influence” of marijuana vary by state, as do applicable punishments. Any amount = under the influence. In some states, any amount of marijuana in the driver’s system will conclusively establish that the driver was under the influence. Above the threshold = under the influence. read more