Chapter 4: DUI / DWI Laws

Driving under the influence of alcohol or drugs is one of the most dangerous and reckless decisions a person can make. Impaired driving is a primary factor in thousands of fatal and injury collisions each year, causing preventable tragedies. Washington’s laws are therefore extremely strict, with severe legal, financial, and personal consequences for offenders. Understanding these laws is not just for the knowledge test; it is a critical component of responsible driving that saves lives.

In Washington, it is a criminal offense to operate a motor vehicle while under the influence of intoxicating liquor, marijuana, or any drug that impairs driving ability. The state’s laws are designed to remove impaired drivers from the road through a combination of administrative license actions and criminal court penalties. These laws apply to all substances that affect a driver’s judgment, reaction time, and coordination, including prescription and over-the-counter medications.

DUI & Implied Consent

A driver can be arrested for DUI based on impairment from any substance. Law enforcement uses chemical tests to measure the amount of alcohol or drugs in a driver’s system, but a conviction can also be based on evidence of unsafe driving.

Defining DUI

A person is considered to be Driving Under the Influence (DUI) if they are driving while affected by alcohol, drugs, or a combination of both. This includes illegal drugs, marijuana, prescription medications, and even some over-the-counter drugs if they impair the ability to drive safely.

BAC and THC Limits

Washington has “per se” laws, which means it is automatically illegal to drive with a Blood Alcohol Concentration (BAC) or THC concentration at or above a specific level.