New Jersey’s driving while intoxicated (DWI) statute is not limited to impairment due to alcohol. The text of the statute also includes “narcotic, hallucinogenic or habit-producing drug[s]” as substances that could cause impairment. The statute specifies a measurable amount of alcohol in one’s system that creates a presumption of impairment, but it does not do the same for any other drugs. This requires prosecutors to rely largely on eyewitness evidence from arresting officers, who may or may not have training in recognizing the signs of impairment by specific substances. If the alleged substance is illegal under state or federal drug laws, this might assist prosecutors. As more and more states pass laws allowing the use of marijuana for medical or recreational purposes, though, the issue is becoming more complicated. New Jersey may consider legislation to allow recreational marijuana use later in 2018, so law enforcement will have to address this issue soon.
The New Jersey DWI statute establishes two methods of proving impairment. One method, sometimes known as “per se DWI,” presumes impairment if a defendant’s blood alcohol content (BAC) was at least 0.08 percent soon after they were allegedly operating a motor vehicle. The “implied consent” statute authorizes police to collect breath samples from anyone driving on New Jersey roads upon suspicion of DWI, and it makes refusal a separate traffic offense. Blood and urine samples may also indicate BAC, but these usually require a warrant or consent. The lack of any statutory guidelines for any drug other than alcohol means that prosecutors must pursue the other form of DWI, which requires proof of driving “while under the influence” of any of the list of substances mentioned earlier. Unlike BAC levels, this is a much more subjective question.
Some states have laws or regulations that specify an amount of marijuana, or other drugs, in one’s system that creates a presumption of impairment. For marijuana, the measurement is in nanograms of THC, the active component of marijuana, per milliliter of blood. Colorado, which was the first state to allow recreational use of marijuana, has set a limit of five nanograms per milliliter. In Pennsylvania, the “legal limit” for marijuana is one nanogram per milliliter. A debate is ongoing among scientists as to whether these numbers have any useful meaning with regard to impairment.