Driving While Stoned: Saliva Test Coming Soon

By Andrew Chow, Esq. on April 18, 2012 | Last updated on March 21, 2019

Will roadside marijuana testing soon be as common as alcohol breath tests? States are debating the issue of how to deal with stoned drivers, as scientists work on a new roadside saliva test for THC, the psychoactive ingredient in pot.

Currently, all states prohibit driving under the influence of controlled substances, including alcohol and marijuana, the Associated Press reports. This applies even if a driver is a medical marijuana patient.

But only a few states impose specific limits on blood or urine THC levels for drivers who are stoned, according to the National Organization for the Reformation of Marijuana Laws. Those states are:

  • Nevada, which limits drivers to THC levels of 2 nanograms per milliliter of blood, or 10 ng/mL of urine. Nevada also sets limits for a byproduct of marijuana metabolism, THC-COOH: 5 ng/mL for blood, and 15 ng/mL for urine.
  • Ohio, which also imposes a limit of 2 ng/mL for THC blood tests, and 10 ng/mL for THC urine tests. For the marijuana metabolite THC-COOH, Ohio's limit is 50 ng/mL in blood and 35 ng/mL in urine; the limits are lower if the metabolite is detected along with alcohol or other drugs.
  • Pennsylvania, which effectively imposes a 1 ng/mL limit for THC or THC metabolites in a driver's bloodstream, according to NORML.

At least seven other states have "zero tolerance" policies for driving while stoned on marijuana: Arizona, Georgia, Illinois, Indiana, Iowa, South Dakota, and Utah.

All remaining states make it illegal to drive under the influence of drugs like pot, but many do not require drivers to undergo a drug test. In lieu of a drug test, a police officer's observation that a driver's ability to drive was impaired by drug use may come into play.

That may soon change, however. Government scientists are developing a roadside saliva test to check for recent marijuana use, the AP reports. The saliva THC test is in its final phases of testing.

Further, two states, Washington and Colorado, will be voting on marijuana decriminalization measures in November, according to the AP. Washington's proposed law would set the blood-THC limit at 5 ng/mL for driving while stoned, according to the AP.

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