DUI Laws

Is there a legal level of alcohol to drive?

Every state in the U.S. and the District of Columbia now have per se drunk driving laws on the books for a DUI arrest. Those laws state that any driver found to have a blood-alcohol concentration (BAC) of 0.08 percent or greater is guilty of driving under the influence. In 2019, the state of Utah lowered the legal blood alcohol limit for driving to 0.05, the strictest in the nation.

"Per se," is a Latin phrase that means "by itself." In other words, having a 0.08 BAC by itself means that you are guilty of driving while intoxicated without regard to any other evidence. The per se DUI laws work much the same as the zero tolerance for underage drivers. Every state also has a law making it illegal for someone under the age of 21 to drive with any level of alcohol in their system.

Impairment is not based on a specific level of alcohol for all individuals.

It is illegal to drive when a person is under the influence of or affected by alcohol and/or drugs. In other words, a person is guilty of DUI if his or her ability to drive is lessened to any appreciable degree, regardless of the quantity of alcohol or drugs in their system.

This means that a person who blows below .08 may be arrested, charged, and convicted of DUI. It also means that a person with no alcohol in their system, but who has some quantity of drugs in his or her system, including prescription medications, may be convicted of DUI.

People feel a great sense of frustration when they find out that the evidence presented against them includes the subjective opinion of the arresting police officer. The testimony is often bolstered by reference to roadside tests, otherwise known in law enforcement circles as field sobriety tests.

There are three methods of BAC testing normally used in the U.S., the most accurate method being a blood test. However, blood tests are inconvenient and invasive; a blood sample must be drawn from subjects’ veins in a hospital or clinical setting. The legality of blood tests and if the police need a warrant to administer one was a topic for the Supreme Court in 2016, and due to implied consent laws states have added roadside blood testing on a county wide basis.

Still, breath tests using handheld devices, also called breathalyzers and "preliminary breath testers" (PBT), are employed most often in the field by law enforcement to assess BAC because they are lightweight, portable, and easy to administer.

While breath test results may help an officer establish probable cause for a DUI arrest, they are not admissible in court (California is among the exceptions). But they often trigger an arrest, which leads to a test on another machine at the police station. That result determines whether someone is charged — and, often, whether they’re convicted.

Law enforcement agencies have struggled for decades with calibrating breathalyzer technology and recent revelations show how unreliable the process has always been.

“Those tests — a bedrock of the criminal justice system — are often unreliable, a New York Times investigation found. The devices, found in virtually every police station in America, generate skewed results with alarming frequency, even though they are marketed as precise to the third decimal place. Judges in Massachusetts and New Jersey have thrown out more than 30,000 breath tests in the past 12 months alone, largely because of human errors and lax governmental oversight. Across the country, thousands of other tests also have been invalidated in recent years.” – New York Times, Nov. 3, 2019

You can learn about the specific DUI laws and penalties for all 50 states here.