In January, Colorado became the first state to legalize recreational marijuana. In March, Colorado became the first state to televise entertaining public service announcements about the danger of driving under the influence of marijuana. The commercials are part of the Colorado Department of Transportation's new campaign: "Drive High, Get A DUI". Although Colorado is one of only two states to legalize recreational marijuana, it is not the only state to criminalize operation of a vehicle under the influence of marijuana. Contrasting Colorado's handling of DUI marijuana with that of Ohio illustrates the deficiencies in Ohio's approach.
In both states, the law makes it illegal to drive a vehicle under the influence of marijuana. Both states have a 'limit' of five nanograms of marijuana metabolite per milliliter of blood. Sounds the same, right? Not exactly. Ohio's laws are different in at least three ways.
First, the states are measuring different stuff. Colorado measures active THC, the constituent of the cannabis plant that has psychoactive side effects. Ohio allows for measurement of any metabolite, and crime labs regularly measure an inactive metabolite which has no psychoactive effects.