When most people think of I-502 they think of the decriminalization of marijuana possession. However, part of the new law also prohibits driving a motor vehicle when a person has over 5 nanograms of THC in their system. It is very difficult to tell if a person is under the influence of marijuana. This has lead to considerable guess work on the part of law enforcement when it comes to making an arrest. Criminal defense lawyers are challenging such arrests. Much of the discussion surrounds the procedures used by a police officer for determining if a person is impaired by marijuana. Unlike with alcohol intoxication, the appearance of a “stoned” driver is not widely known.
Another important part of the new law is that there is no exception to the 5 nanogram limit for medical patients using marijuana. This provision is unpopular for many medical patients who feel that due to their tolerance level, they can safely drive with 5 nanograms of THC in their blood. A difficult part of the new law is that a user of marijuana never has a good way of knowing how high their THC level is. This is in contrast with alcohol, where charts are available for predicting blood alcohol levels based on body weight and alcohol intake.