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Driving While Impaired | Arizona DUI

IMPAIRED TO THE SLIGHTEST DEGREE | ARIZONA DUI

The Ultimate Guide

Impaired to the Slightest Degree

If you are arrested for DUI, Extreme DUI, or Super-Extreme DUI most likely these charges include and allegation that you were impaired to at least the slightest degree.  Here is what it means to be “impaired” under an Arizona DUI law.

Impaired as a Matter of Law

Arizona law has created two ways to violate the first offense DUI laws. Accordingly, in Arizona DUI means:

  • Driving while impaired to the slightest degree by alcohol or a drug; or
  • Having an alcohol concentration above a statutory limit within 2 hours of driving.

So, how do you define “impaired to the slightest degree”?  Let’s find out.

In the beginning…

What Does Being Impaired Mean?

The legislative history of Arizona’s DUI law (A.R.S. 28-1381) does not tell us the reason why they left such an important term up for interpretation. While there were probably several reasons, one seems fairly obvious, once you understand what impairment really means in the context of alcohol consumption.

You cannot determine if a person is impaired at performing a task (like walking, standing on one leg, or dancing) unless you know how they normally perform that task – without consuming alcohol. That being said, we know it does not mean driving while intoxicated.  It is a lower threshold.

More on this below.

Under the Influence v. Impaired

The law makes an important, but often overlooked, distinction between being under the influence of alcohol and driving while impaired. Let’s look at the DUI law. The jury instructions in a DUI case where a person is alleged to have been driving impaired by alcohol: 

Arizona DUI First Offense Laws

There are three essential elements of a first offense Arizona DUI:

Notice that the proof of a person was under the influence of alcohol is not sufficient to make them guilty of the DUI.  To illustrate, you can consume alcohol resulting in a flushed face or a feeling relaxed.  That is just being under the influence of an intoxicating beverage.  However, impairment goes beyond those effects.

Your Specific Baseline

The effects of alcohol on the human body are studied by Toxicologists.  In the field of toxicology, impairment is defined as a measurable difference between the way a person normally performs a task, and how they perform the same task less effectively, because of the consumption of alcohol.  

To determine if any form of impairment is present you need to know what a person’s baseline abilities are for that task.  A police officer who meets you for the first time – during a traffic stop – has no way to know your baseline motor skill abilities for any given task.

Stages of Alcohol's Effects

Dr. Kurt Dubowski was considered one of the foremost expert’s regarding the effects of alcohol on the human body. In 1953, he conceived and subsequently published a chart illustrating the stages of Alcohol Influence that is still used today in impaired driving cases.  His BAC interpretation table was updated in 2012.

Here is a downloadable copy of the Dubowski Chart

The Progression of Alcohol's Effects

The specific effects – of a specific alcohol concentration – will vary to some degree from person to person. However, the order of things effected by alcohol in the human body always remains the same.  It’s a rigid progression.  If the observed symptom do not fit this progress then alcohol is likely not the cause of the impairment.

Progression of Alcohol Impairment

To determine if any form of impairment is present you need to know what a person’s baseline abilities are for that task.  A police officer who meets you for the first time – during a traffic stop – has no way to know your baseline motor skill abilities for any given task. 

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