What is the Per Se DUI Law, and How Does It Affect Me?


Most people know that if you drive with a BAC level of .08 or more, you are considered intoxicated by law.  However, this hasn’t always been the case.

The Per Se Law History

In 1982, Congress created a series of grant programs designed to encourage states to enact strong, evidence-based impaired driving laws.  One such law was a .10 BAC per se law.

Per se is Latin for “by itself,” meaning inherently.

Regardless of how much alcohol you thought you drank, if your BAC level was at .10 or more, you were considered intoxicated by law.  No further evidence of intoxication or impairment needed to be demonstrated for purposes of a DUI case.

This is important because regardless of how “sober” you believe you may be, it is your BAC that matters in the eyes of the law once you get behind the wheel of your car.  If your BAC exceeds the legal limit, you are legally presumed to be impaired.

In 1998, President Clinton set new standards to reduce the significant number of alcohol-related injuries and deaths that occur on America’s roadways.  Among the measures introduced was a reduction in the per se legal limit from .10 to .08.

Today, every state has a legal per se limit of .08 for drivers 21 years of age or older. Underaged drivers are faced with an even more strict “zero tolerance” law that makes it illegal for a person under the legal drinking age to have any amount of alcohol concentration in their blood.

Why Do We Have the .08 Per Se Law?

The per se limit is based upon years of scientific data and clinical and behavioral research that established the various stages of alcoholic influence.

Driving a vehicle requires the driver to perform divided tasks.  To safely operate a motor vehicle, the driver must simultaneously read street signs, work the brake or gas pedal, turn the steering wheel, make judgments about the intent of other vehicle traffic, bicyclists and pedestrians, all in a fraction of a second.

At varying levels, alcohol affects all the skills required to safely operate a motor vehicle.  The per se law makes it easier for the prosecution to establish that you were impaired without requiring much testimony by the arresting officer about what their training, education and experience led them to conclude about your level of impairment.

Because of this law, drunk driving fatalities have declined since 2005. Back then, 13,592 lives were lost. In 2013, it lowered to 10,076.

Based upon research on the effectiveness of per se laws, the National Transportation Safety Board recommended lowering the per se limit from .08 to .05 BAC in 2017.  Utah became the first state to enact this legislation.

Strong DUI Laws Make a Difference

Even more lives can be saved if the per se law continues to be in effect, especially when drunk driving fatalities are sadly increasing.

Another law that helps keep our roads safe are Ignition Interlock requirements.

The states that order Ignition Interlocks for all DUI offenders, rather than only repeats, see less drunk driving fatalities. In addition, repeat drunk driving decreases if first-time offenders use an Ignition Interlock.

With strong DUI-related laws, such as the .08 per se law and Ignition Interlock requirements, a positive change can happen throughout our roadways.

Toby Taylor


Guest Contributor
Toby Taylor
Smart Start Vice President of Regulatory Compliance

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