Impairment (Under the Influence)
Impairment, which statutes such as Nebraska's describe as being "under the influence," is a basis for a DUI or DWI charge that rests on the effect of alcohol or drugs on a person rather than on a measured concentration alone. Nebraska's statute, for example, lists being under the influence of alcoholic liquor or of any drug as a ground separate from its blood and breath concentration grounds.
DUI and DWI statutes can describe the offense in more than one way. One way is a measured concentration of alcohol or another substance. Another is impairment, often phrased as being "under the influence" or "intoxicated," which focuses on the effect a substance has on the person. The examples below come from the statutes of Nebraska, Virginia, Montana and Arkansas.
How is impairment different from a measured concentration?
A concentration ground turns on a measured amount of alcohol or another substance. An impairment ground turns on whether the person was under the influence. Nebraska's statute, Neb. Rev. Stat. § 60-6,196, shows the distinction: it makes it unlawful to operate or be in actual physical control of a motor vehicle while under the influence of alcoholic liquor or of any drug, and it lists separate grounds based on blood and breath alcohol concentration.
Arkansas's statute, A.C.A. § 5-65-103, takes a similar structure with different wording. It makes it unlawful for a person who is intoxicated to operate or be in actual physical control of a motor vehicle or a motorboat on the waters of the state, and it separately addresses alcohol concentration in breath or blood.
How do statutes describe the degree of influence?
Virginia's statute, Va. Code § 18.2-266, lists several alternatives. One is driving or operating while under the influence of alcohol. Others cover narcotic drugs or other self-administered intoxicants or drugs, and the combined influence of alcohol and drugs, each to a degree which impairs the person's ability to drive or operate a motor vehicle, engine or train safely.
The same Virginia statute provides that a charge alleging a violation of it can support a conviction under any of its listed alternatives, including both the influence grounds and the concentration grounds.
What evidence can bear on whether a person was under the influence?
Montana's statute, Mont. Code Ann. § 61-8-1002, defines driving under the influence to include driving or being in actual physical control of a vehicle on the ways of the state open to the public while under the influence of alcohol, any drug, or a combination of alcohol and any drug. The statute also sets out rebuttable inferences tied to test results, and it states that those provisions do not limit the introduction of any other competent evidence bearing on whether the person was under the influence.
On the mental element, Arkansas's statute states that an alcohol-related offense under it is a strict liability offense, and Montana's statute imposes absolute liability as provided in a separate section of Montana law. A lawyer in the reader's state can explain how these provisions apply to a particular charge.
The figures for your state
Deadlines, limits and penalty ranges are set by each state’s statutes, so this page does not state them. Each state page shows them with the official source and the date they were verified — or says plainly that a figure has not been confirmed yet.
Common questions
Is an impairment charge limited to alcohol?
Not in every statute quoted here. Nebraska's statute covers alcoholic liquor or any drug, Montana's covers alcohol, any drug or a combination, and Virginia's addresses alcohol, drugs and their combined influence. Arkansas's statute uses the word intoxicated, and the excerpt here does not define that term.
Does the impairment ground apply only to cars?
The wording varies by state. Arkansas's statute covers motor vehicles and motorboats on the waters of the state. Virginia's covers any motor vehicle, engine or train, and it treats mopeds operated on the public highways of the state as motor vehicles.
Can the impairment and concentration grounds appear in the same statute?
Yes, in each statute quoted here. Nebraska, Virginia, Montana and Arkansas each list an influence or intoxication ground alongside concentration-based grounds in the same section.
Sources
- Neb. Rev. Stat. § 60-6,196 (official source, opens in a new tab)Driving under influence of alcoholic liquor or drug; penalties.
- Va. Code § 18.2-266 (official source, opens in a new tab)Va. Code § 18.2-266 - Driving motor vehicle, engine, etc., while intoxicated, etc
- Mont. Code Ann. § 61-8-1002 (official source, opens in a new tab)Driving Under Influence
- A.C.A. § 5-65-103 (official source, opens in a new tab)A.C.A. § 5-65-103 — Driving or boating while intoxicated.
These sources are cited for the jurisdiction and scope identified on this page. They do not establish the law of another state.
Related
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