Chapter 4: DUI / DWI Laws

Use this guide to prepare for the exam, and refer to the official manual for complete details.

Driving is a privilege that requires a driver’s full attention and unimpaired judgment. Driving Under the Influence (DUI) of alcohol or drugs is a leading cause of traffic fatalities and injuries, and Delaware enforces some of the strictest laws in the nation to combat it. Understanding these laws, from the legal definition of impairment to the severe administrative and criminal penalties, is critical for ensuring personal safety, protecting others, and avoiding life-altering legal consequences.

In Delaware, a person is guilty of Driving Under the Influence (DUI) if they drive, operate, or have actual physical control of a vehicle while under the influence of alcohol, any drug, or a combination of both. This law applies not only to public highways but to any location within the state, including private property. The “drug” component includes illegal substances, prescription medications, and over-the-counter drugs that can impair driving ability.

Blood Alcohol Concentration (BAC) Limits:

BAC is the percentage of alcohol in a person’s bloodstream. Delaware law establishes specific BAC levels at which a driver is legally considered impaired.

A chart compares four standard drinks—1.5 ounces of whiskey, 5 ounces of wine, 8–9 ounces of a cocktail, and 12 ounces of beer—indicating they are equivalent in alcohol content.
  • Drivers 21 and Over: A BAC of 0.08% or greater is considered per se evidence of DUI. This means a driver can be convicted based on the BAC level alone, without further proof of impairment. However, a driver can still be arrested and convicted for DUI with a BAC below 0.08% if their ability to drive safely is impaired.
  • Drivers Under 21 (Zero Tolerance Law): Delaware has a “Zero Tolerance” law for underage drivers. Anyone under the age of 21 who drives with a BAC of 0.02% or greater will have their license revoked. This low threshold accounts for trace amounts of alcohol from sources like mouthwash while making it illegal to consume alcohol and drive.
  • Commercial Drivers (CDL): A person operating a Commercial Motor Vehicle (CMV) is subject to a stricter limit of 0.04% BAC. A conviction at this level will result in a disqualification of their commercial driving privileges.

Implied Consent Law:

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