Definition of driving under the influence of alcohol according to Illinois law

by Sami Azhari on October 9, 2010

Definition of Under the Influence | Illinois DUI Laws

Driving under the influence can be charged in numerous ways under Illinois law. It can be based on impairment by illegal drugs, prescription medication, and the combined influence of alcohol and drugs. But the most prevalent charge of DUI is based on intoxication by alcohol.

If a person is accused of driving under the influence of alcohol, he will be charged in any of the following two ways:

  1. Having an alcohol concentration of 0.08 or more in the person’s blood or breath.
  2. Being under the influence of alcohol.

An alcohol concentration of 0.08 or more (that is, anything more than 0.079) is presumptively under the influence of alcoh0l. The law uses a Latin term to describe this offense: per se. The definition of per se is “of, in, or by itself or oneself; intrinsically.” A person is per se guilty of DUI if they blow a 0.08 or above. The per se charge is section 11-501(a)(1) of the vehicle code.

The second way of charging DUI occurs where there is no chemical test (such as a breathalyzer). A person who refuses to blow cannot be charged with the per se violation under 11-501(a)(1). The Illinois DUI statute provides that a person who is not per se is still in violation of the law if that person is “under the influence of alcohol.” See 625 ILCS 5/11-501(a)(2).

(625 ILCS 5/11-501) (from Ch. 95 1/2, par. 11-501)

Sec. 11-501. Driving while under the influence of alcohol, other drug or drugs, intoxicating compound or compounds or any combination thereof.

(a) A person shall not drive or be in actual physical control of any vehicle within this State while:

(1) the alcohol concentration in the person’s blood or breath is 0.08 or more based on the definition of blood and breath units in Section 11-501.2;

(2) under the influence of alcohol;

The statute does not define what it means to be under the influence of alcohol. The only definition is found in the jury instructions approved by the Illinois Supreme Court.

DUI is a criminal offense and, as such, the defendant is entitled to a trial by jury of 12 people. When the trial takes place, the jury would hear the evidence and receive instructions as to the law. The actual statute book containing the law is not provided. Rather, only the instructions are provided.

Jury instructions are based on Illinois Pattern Instructions (IPI), and these are approved by the state high court. IPI 23.29 provides the following:

Definition Of Under The Influence Of Alcohol

A person is under the influence of alcohol when, as a result of drinking any amount of alcohol, his mental or physical faculties are so impaired as to reduce his ability to think and act with ordinary care.

The issue for the jury to decide is whether the defendant was able to think and act with ordinary care. The definition enables the defendant to argue reasonable doubt. Ordinary care is similar to a negligence standard.

For example, if there was no traffic accident, then arguably the driver was able to exercise ordinary care.

But this is not to be confused with the prosecution’s burden of proof beyond a reasonable doubt. While a person may be guilty for failing to be able to operating a motor vehicle with ordinary care, the prosecution has to prove this fact beyond a reasonable doubt.

If the driver did not commit any moving violations, there should be reasonable doubt that he was not able to exercise ordinary care. Where there is an accident in play, the case may be more difficult. But all hope is not lost, because motor vehicle accidents happen all the time with people who are not impaired.

A jury should be receptive to these arguments.

If the defendant proceeds with a bench trial, the judge has a duty to follow the law, just like a jury. It is a matter of judgment whether to waive a jury, because both a jury trial and bench trial have their own risks.

Previous post:

Next post: