What Laws Govern Stoned Driving?

By Cynthia Hsu, Esq. on July 08, 2011 | Last updated on March 21, 2019

Drunk driving laws are in every state. But, what laws govern stoned driving and driving under the influence of drugs?

While "driving under the influence" tends to conjure up images of drunk driving, most people don't realize that "driving under the influence" also encompasses driving under the influence of drugs that may impair a person's ability to drive and operate a car.

Driving while under the influence of drugs - legal and illegal - can result in a DUI charge, even if the drugs are doctor prescribes the pills.

But, how much drugs is considered too much and over the legal limit? This is where the law governing stoned driving becomes a bit tricky.

Unlike alcohol, it's often difficult to detect how much drugs are in a person's system at a traffic stop. Alcohol can be measured via breathalyzer tests, which are considered relatively accurate.

Drugs like marijuana, however, are not as easily detectable. Marijuana is detectable usually via blood or urine tests - something that is not easily administered during routine traffic stops.

As a result, many states have enacted "per se" laws about drugged driving. Essentially, these "per se" laws mean that it is illegal to operate a vehicle with any detectable amount of drugs in your system at the time. Some states have a zero tolerance policy, while others have certain limits that must be met before a person has violated the law.

About 19 states have "per se" laws about driving while under the influence of prohibited substances or other drugs. About two of these states have incorporated these laws with drunk driving statutes.

And, a further 47 states have laws that create Drug Evaluation Classification or Drug Recognition Experts who are trained to detect drug impairment. These experts are trained to notice eye moments and other behaviors which may indicate drug use.

Even if a state does not have a "per se" law prohibiting stoned driving or driving under the influence of drugs, doing so is dangerous and should be avoided. When a person is impaired while driving, all motorists and passengers sharing the road may be in danger.

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