Dale Gieringer of California NORML cites two recent studies that highlight the folly and unfairness of "zero tolerance" laws against driving "under the influence" of illegal drugs. Such laws treat drivers with any trace of marijuana in their systems as if they were intoxicated, even if they smoked a joint days before and are not impaired at all.
One study, published in the September Proceedings of the Association for the Advancement of Automotive Medicine, found that injured drivers whose urine tested positive for marijuana were no more likely to have contributed to the accident that injured drivers who tested negative. "An important reason for the negative findings in this study is that it relied on urine tests to determine the presence of marijuana," Gieringer notes. "Urine commonly tests positive for marijuana metabolites for days after use, long after any impairing effects of THC have faded. Those studies which have detected a negative impact of marijuana use on accident risk have relied on blood tests for THC, which are far more sensitive to recent use within the past couple of hours. "
The other recently reported study, which was commissioned by the French government, confirmed positive urinalysis results with blood tests. It found that drivers under the influence of marijuana were somewhat more likely to be culpable for accidents than drivers who had not used drugs, but not nearly to the same extent as drivers under the influence of alcohol. According to a report in Liberation (for which Gieringer provided a translation), the results indicate that "the risk of being responsible for a fatal accident under cannabis alone is weak, though not zero. The risk isn't in any case worse than that of a driver with between 0.02 and 0.05 blood alcohol content." The results are embarrassing to the French government, which in 2003 adopted a double standard that sets the legal blood content limit for driving at 0.05 percent for alcohol but zero for marijuana.
To get an idea of what "zero tolerance" would mean if it were applied to alcohol, read this eye-opening, infuriating Washington Post article (link courtesy of Mr. Nice Guy) about D.C.'s approach to DUI enforcement. It tells the story of Debra Bolton, an Alexandria, Virginia, lawyer who was handcuffed, arrested, jailed, and nearly forced into an alcohol re-education program because she had a glass of wine at a restaurant. The resulting BAC was 0.03 percent, less than half the legal limit in the rest of the country. "In Maryland and Virginia, as in other states, drivers generally are presumed not to be intoxicated if they test below .05," the Post notes. The paper quotes a toxicologist who disputes the arresting officer's contention that Bolton displayed signs of drunkenness: "There's no way possible she failed a test from impairment with a .03."