The number of marijuana-impaired drivers on the roads of California and other U.S. states has increased by a worrying 50 percent in just seven years according to a report from the National Highway Traffic Safety Administration. The agency's most recent National Roadside Survey of Alcohol and Drug Use by Drivers also reveals that THC, which is the chemical compound in marijuana that gives the drug its intoxicating properties, was found in the blood or oral fluid samples collected from 13 percent of the nighttime drivers who took part in the study and 9 percent of the drivers who were tested during daylight hours.
NHTSA began conducting National Roadside Studies in the 1970s to help lawmakers and police departments better understand and combat drunk driving. While NHTSA figures indicate that the number of drivers impaired by alcohol has fallen by 77 percent since 1973, marijuana use by motorists is on the rise according to the federal road safety watchdog. Experts believe that laws passed in states like California that permit the use of marijuana for recreational or medical purposes may be contributing to the problem.
Marijuana impairment provides road safety advocates, legislators and police departments with a number of thorny issues. THC and alcohol affect the human body in different ways, and scientifically accepted techniques used to identify drunk drivers may be of little value when marijuana use is suspected. Traces of THC can also be detected in blood samples days or even weeks after its intoxicating effects have waned.
Experienced criminal defense attorneys may study police reports particularly closely when their clients have been accused of driving under the influence of marijuana. Prosecutors must prove drunk driving charges beyond reasonable doubt, and this could be challenging without accepted scientific THC testing protocols and compelling toxicology evidence.