Cannabis products are becoming increasingly legal, many states have trouble drawing the line of “impairment.” In Colorado, an individual can be charged with a DUI (Driving Under The Influence) if he or she has more than five nanograms of THC (the chemical responsible for marijuana’s physiological effects) per milliliter of blood in their system. The state of Washington also goes by the five nanogram limit. In California, however, there is no set limit on the amount of THC an individual can have in their system. According to The San Francisco Chronicle, if a person is under the influence of marijuana to the point it becomes a traffic concern, one can be charged with a DUI under California law.

In states where cannabis products are legal, some DUI cases can be completely acquitted regardless of their THC levels, according to The San Francisco Chronicle. For example, when Melanie Bringear was pulled over for expired license plates, the officer charged her with a DUI. Bringear’s THC levels were nearly four times the legal limit in Colorado. However, when her case went to court, she was acquitted of her DUI charge. In a statement, Bringear said, “I wasn’t weaving. I didn’t miss a turn signal. They had no proof.” With no proof she was breaking any traffic laws, the jury found Bringear not guilty.

In another case, a San Diego Police Officer made a regular traffic stop. When the officer, John Perdue, pulled over someone who was a regular marijuana smoker, he performed a field sobriety test. The man who was pulled over passed the test with flying colors, despite telling the officer he had smoked cannabis recently, according to The LA Times. With no proof of impairment, Perdue let the man go.

Unlike alcohol, there is no on-site test a person can take to determine a level of impairment. THC levels are largely based on how someone appears and acts. With marijuana becoming increasingly more available for medical and recreational use, how will arresting officers determine whether or not someone is a traffic concern?  What does driving high really mean?