Although it's easy to assume that a defendant charged with DUI or DWI is alleged to have operated a motor vehicle while under the influence of alcohol, most states' statutes are not nearly so specific. In fact, defendants may be charged with (and convicted of) DWI even if the substance they were using prior to their arrest was legally prescribed, including sleeping pills like Ambien, prescription narcotics, or even allergy medication. Read on to learn more about how state DUI and DWI laws govern the use of legal prescription drugs.

What Do DUI Laws Cover?

Although each state's DUI laws are slightly different, as a general rule, they prohibit drivers from operating a motor vehicle, including mopeds and other "non-street-legal" vehicles, on a public thoroughfare while under the influence of an intoxicating substance. Most states will not permit an individual to be arrested for DUI if they're on private property (unless they're trespassing on someone else's property). 

Most DUI laws are broadly written to cover alcohol, illegal drugs (including drugs like marijuana, even in states where this drug is legal), and even legal prescription drugs or supplements if these drugs may result in impairment. 

How Is Intoxication or Impairment Proven When The Drug Used Is Legal?   

While it can be easy for police officers to determine a person's level of alcohol intoxication, since the law prohibits a blood alcohol content (BAC) above 0.08, as well as illegal drug intoxication, which can be assessed through a blood test, a conclusion that an individual is driving while dangerously impaired from a legally prescribed drug can be far tougher. Officers instead need to rely on things like dashcam or body camera video and their own testimony (and any written police reports) on the person's intoxication. 

This means that a criminal defendant facing a DUI charge for using legal drugs has a few potential defenses. If there's no video evidence of intoxication, only the officer's testimony, this testimony may be able to be rebutted by other witness testimony or even just vigorous cross-examination. Meanwhile, absent some scientific evidence that a certain drug results in impairment at certain concentrations in the blood (as with alcohol), a jury may not be willing to believe that the laboratory or hospital report listing the concentration of a prescription drug is enough evidence to find, beyond a reasonable doubt, that the defendant was not in any condition to drive. 

For more information, reach out to a DWI attorney.