As of October, 2015, 23 states and the District of Columbia have legalized medical marijuana. Of these, four states and D.C. have legalized marijuana for recreational use as well. This year, at least three more states are scheduled to vote on measures to legalize marijuana in one form or another. After watching Colorado generate millions of dollars in tax revenue from marijuana sales in just a few years, legislators elsewhere have become more open to the possibility of legalizing pot in their own states.
With legal marijuana use becoming far more widespread, law enforcement agencies are struggling to find reliable ways to determine whether or not drivers are impaired by the drug. The trouble is that measuring marijuana impairment isn’t nearly as straightforward as administering a breathalyzer test. Furthermore, there isn’t a scientific consensus on the extent to which marijuana use impairs a person’s ability to drive.
Currently, DUI testing standards for marijuana vary widely between states where the drug is legal.
Six states have established blood concentration limits for THC, the active ingredient in marijuana. Nine other states have zero-tolerance laws that make the presence of THC metabolites illegal as well. The trouble is that these metabolites can stay in a person’s bloodstream for days or even weeks after the effects of the drug have subsided.
Some states have considered adopting oral swab tests to replace complicated blood and urine tests. Unfortunately, these tests are only reliable indicators of marijuana impairment less than one third of the time they’re used. Because THC lingers in the body long after smoking marijuana, no test – blood, urine or saliva – is able to distinguish current impairment from marijuana use within the last few days.
Recently, a study conducted the AAA Foundation for Traffic Safety raised concerns about the general lack of scientific understanding supporting marijuana DUI tests. The study acknowledged that while there should be established legal limits for marijuana impairment, current testing methods are so unreliable and arbitrary that they put sober drivers at risk of facing DUI charges.
“There is understandably a strong desire by both lawmakers and the public to create legal limits for marijuana impairment in the same manner we do alcohol,” said Marshall Doney, president and CEO of AAA. “In the case of marijuana, this approach is flawed and not supported by scientific research.”
For frequent marijuana smokers, current standards could cause them to positive for impairment any time they drive. As a result, many people with medical marijuana prescriptions are hesitant to drive even when they haven’t ingested the drug recently. In one case, a Colorado woman who was prescribed marijuana for back pain spent 13 months and thousands of dollars fighting DUI charges that she was eventually acquitted of.
Until laboratories are able to provide law enforcement agencies with accurate, reliable testing materials for marijuana impairment, more innocent drivers are likely to face similar frivolous charges in the future. In the meantime, law enforcement agencies will be forced to make DUI arrests based on data that’s questionable at best.