Washington DUI 101: Laws, Limits, and Legal Defenses
Washington Dui Laws Alcohol Cannabis Drugs

In Washington, a person can be charged with driving under the influence (DUI) for driving a vehicle while under the influence of or affected by intoxicating liquor, cannabis, or any drug. The DUI statute, RCW 46.61.502, describes a single offense that a driver might commit by more than one method.

According to the Washington Supreme Court, the statute sets out four “facets” of the same criminal conduct:

“RCW 46.61.502 sets out four ways in which the offense may be committed. The four ways in which the offense may be committed do not, however, create “alternative means” (i.e., distinct types of conduct). The statute sets out four “facets” of the same criminal conduct, driving a vehicle under the “influence of” or while “affected by” certain substances that may impair the driver.” (State v. Sandholm, 184 Wn.2d 726, 364 P.3d 87, 2015)

Key Takeaways

  • Washington’s DUI law prohibits driving under the influence of alcohol, cannabis, or any drug.
  • DUI can be proven by “per se” BAC (0.08+) or THC (5.00+ ng/mL) limits, or other evidence of impairment.
  • DUI laws apply on public highways and most private properties.
  • Defenses are limited but may include challenging test accuracy, drinking after driving, or involuntary intoxication.
  • Prescription use and voluntary intoxication are not valid defenses.

What is the Legal Limit for Alcohol and THC?

A person is considered guilty “per se” of DUI if within two hours after driving they have either:

  • An alcohol concentration of 0.08 or higher (grams of alcohol per 210 liters of breath)
  • A THC concentration of 5.00 nanograms per milliliter (ng/mL) of blood or higher

The breath or blood test must be conducted according to the testing standards in RCW 46.61.506 and the methods approved by the state toxicologist. The prosecutor has the burden of proving beyond a reasonable doubt that the test reading is correct. The reading at the time of the test is considered the reading at the time of driving.

Washington Dui 101 Laws Limits Legal Defenses - Man drinking beer in bar

What Other Evidence Can Show a Driver Was Under the Influence?

Even if a driver’s alcohol or THC levels are below the “per se” limits, they can still be convicted of DUI based on evidence showing they were driving under the influence. Under Washington law, a person is considered “under the influence” if:

“…the evidence is sufficient for the factfinder to infer that the ability to handle an automobile was lessened in an appreciable degree by the consumption of intoxicants or drugs”. (State v. Wilhelm, 78 Wn.App. 188, 896 P.2d 105, 1995)

This essentially means that alcohol, cannabis, or other drugs affected the person’s ability to drive safely to any appreciable degree. Admissible evidence could include:

  • Erratic driving
  • Physical signs of intoxication
  • Field sobriety tests
  • Statements by the defendant
  • Witness testimony

Where Do DUI Laws Apply?

The DUI statute prohibits driving under the influence on public highways and “elsewhere throughout the state.” A highway is defined as the entire publicly maintained roadway when any part is open for public vehicular travel.

DUI laws also apply on private property in many cases. For example, courts have upheld DUI convictions for drivers apprehended in apartment complex parking lots that open to public roads. However, the law may not apply in very limited circumstances on isolated private property, like a rural field not near any public access points.

Washington DUI Laws: 
BAC, THC Limits, & Impairment Evidence - Young white girl smoking marijuana spliff. White hands with pink and grey nails

Are There Any Defenses to DUI Charges?

There are some limited defenses available in DUI cases:

  • Challenging test accuracy: A defendant can challenge the accuracy of BAC or THC test results. The burden is on the prosecutor to prove the reading is correct.
  • Drinking after driving: It is an affirmative defense if the defendant can prove by a preponderance of evidence that they consumed alcohol after driving but before the test, causing the “per se” BAC result. The defendant must notify the prosecutor before trial of their intent to raise this defense.
  • Involuntary intoxication: Unconscious, involuntary intoxication (such as from innocently taking a spiked drink or prescribed medication) may be an affirmative defense the defendant can raise, but they bear the burden of proof.

Notably, the following are not valid defenses to a DUI charge in Washington:

  • Having a prescription for the substance that caused impairment
  • Voluntary intoxication
  • Pulling over safely before law enforcement contact (only a defense to Physical Control charges)

In summary, Washington’s DUI law is violated whenever a person drives a vehicle while under the influence of alcohol, cannabis, or any drug to a degree that lessens their ability to drive safely. The statute provides “per se” alcohol and THC limits but also allows conviction based on other evidence of impairment. Drivers should be aware that DUI laws apply broadly on public and most private roadways. While there are some limited defenses available, the state’s DUI statute is generally strictly enforced.

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Source: 2023 Driving Under the Influence (DUI) Benchbook, Judge Linda S. Portnoy (ret.), Editor