Washington Per Se DUI Laws

Many people charged with DUI in Washington do not fully understand the concept of a “per se” DUI. Under Washington law, you can be convicted of DUI based solely on the concentration of alcohol or THC in your system — even if the State does not prove actual impairment.

This is known as a per se DUI.

Under RCW 46.61.502 (DUI) and RCW 46.61.504 (Physical Control), a person is guilty of DUI if, within two hours of driving, they have:

  • A blood alcohol concentration (BAC) of 0.08% or higher, OR
  • A THC concentration of 5.00 nanograms per milliliter of whole blood or higher.

In per se cases, the chemical test result itself becomes the primary evidence.

Alcohol Per Se DUI in Seattle

Washington's legal BAC limits are:

  • 0.08% for drivers age 21 and over
  • 0.04% for commercial drivers operating a commercial vehicle
  • 0.02% for drivers under age 21

If a properly administered breath or blood test shows a BAC at or above these limits within two hours of driving, the State can charge DUI without separately proving visible impairment.

Breath testing procedures are governed by RCW 46.61.506 and strict technical requirements. Errors in testing, machine calibration, or administration can provide grounds for defense.

Marijuana Per Se DUI in Washington

Washington is one of the few states with a defined per se THC limit.

A driver may be charged with DUI if a blood test taken within two hours of driving shows:

  • 5.00 nanograms or more of THC per milliliter of whole blood.

Unlike alcohol, THC can remain detectable in the bloodstream long after impairment has subsided. Because of this, marijuana per se cases often involve complex scientific and evidentiary challenges.

Per Se DUI vs. “Affected By” DUI

Washington DUI law allows prosecutors to proceed under two separate theories:

  • Per Se DUI – Based strictly on chemical test results.
  • Affected By DUI – Based on officer observations of impairment.

Even if a chemical test is below the per se limit, a person may still be charged if the State claims they were “affected by” alcohol or drugs.

Penalties for Per Se DUI in Washington

The penalties for a per se DUI conviction are the same as any other DUI conviction under RCW 46.61.5055. Depending on prior history and BAC level, penalties may include:

  • Mandatory jail time
  • Substantial fines
  • License suspension or revocation
  • Ignition interlock device requirement
  • Alcohol or drug evaluation and treatment
  • Probation supervision

Additionally, you have only 20 days from the date of arrest to request a Department of Licensing hearing to challenge your administrative license suspension.

Defending a Per Se DUI Charge in Seattle

Although per se DUI cases rely heavily on chemical testing, these cases are not automatic convictions. Defense strategies may include:

  • Challenging breath machine calibration
  • Questioning blood draw procedures
  • Examining chain of custody issues
  • Attacking timing and two-hour rule compliance
  • Raising scientific reliability concerns

Attorney Steve Karimi is a former prosecutor who understands how DUI cases are built and how to challenge weaknesses in chemical testing evidence.

Call a Seattle Per Se DUI Defense Lawyer Today

A chemical test result does not mean your case is hopeless. Early legal intervention can significantly impact the outcome.

Call 206-222-3280 now for a free consultation. Available 24/7.