Missouri residents who have been stopped for drunk driving may be familiar with the standard panel of field sobriety tests. An officer will likely require drivers to follow a pen with their eyes, walk in a straight line and stand on one leg for 30 seconds. Drivers who complete those tests without incident are likely not intoxicated. So far, though, tests do not exist to accurately predict whether a stoned driver should face a DWI charge. With a growing number of states loosening marijuana restrictions, the issue of drugged driving is reaching the forefront of many legal jurisdictions.

Research shows that just 30 percent of stoned people will fail a standard field sobriety test. In most instances, that test is only useful for drivers who are not used to being intoxicated on marijuana; about 50 percent of the less-frequent consumers were tripped up by the test. Scientists say they are still not sure how to interpret these numbers, as stoned drivers are decidedly different from those who have been drinking. Still, with an estimated 6 percent of American drivers stoned behind the wheel, legislation must examine potential consequences and penalties for those accused of drugged driving.

Few would argue that marijuana intoxication causes cognitive impairment that reduces driving safety. Still, that effect may be far lower than the danger posed by those who are drunk behind the wheel. Those with THC in the bloodstream are only twice as likely to get in a wreck, while younger drivers experience a 20-fold increase in fatal accident risk. Stoned drivers tend to drive slower and more conservatively.

Scientists have not yet discovered a reliable test that correlates THC levels in the body with cognitive impairment. Many say that it might not be necessary to focus on stoned drivers, though, considering the higher numbers of drunk drivers on Missouri roads. Drivers who are facing DWI offenses may be subject to more severe penalties if they are found driving while stoned and drunk at the same time, but it appears that researchers are pushing for leniency and caution when evaluating potential consequences for those who test positive for THC.

Source: The New York Times, “Driving Under the Influence, of Marijuana” Maggie Koerth-Baker, Feb. 17, 2014