DUI Sobriety Testing in Seattle

When law enforcement officers in Washington suspect a driver of being under the influence, they may conduct a series of tests to evaluate impairment. These tests are generally divided into two categories: field sobriety tests and chemical tests.

Sobriety testing plays a central role in DUI investigations and often becomes key evidence in court.

Field Sobriety Tests (SFSTs)

Field Sobriety Tests are roadside physical exercises designed to evaluate coordination, balance, and the ability to follow instructions. These tests are used before an arrest is made to help determine whether probable cause exists for DUI.

The National Highway Traffic Safety Administration (NHTSA) recognizes three Standardized Field Sobriety Tests (SFSTs):

  • Horizontal Gaze Nystagmus (HGN): The officer observes the eyes for involuntary jerking while the suspect follows an object. Alcohol can exaggerate nystagmus.
  • Walk-and-Turn Test: The suspect walks heel-to-toe along a straight line, turns, and walks back while following detailed instructions.
  • One-Leg Stand Test: The suspect stands on one leg for approximately 30 seconds while counting aloud.

These tests are often recorded on body camera or dash camera video. They are subjective in nature and can be influenced by fatigue, medical conditions, anxiety, uneven surfaces, footwear, or weather conditions.

Important: In Washington, drivers are not legally required to perform field sobriety tests. There is no direct license suspension penalty for refusing roadside physical tests.

Chemical Testing: Breath and Blood

Chemical testing is used to measure alcohol or drug concentration in the body.

Breath Testing

Breath tests measure alcohol concentration only. Under Washington's Implied Consent Law (RCW 46.20.308), a driver who is lawfully arrested for DUI is deemed to have consented to a breath test.

A breath test result of 0.08% or higher (0.02% if under 21) may support a per se DUI charge.

Blood Testing

Blood testing is typically used in cases involving suspected drug impairment, including marijuana. In Washington, a THC concentration of 5.00 ng/mL or higher within two hours of driving may support a per se marijuana DUI charge.

Blood draws generally require a warrant unless voluntary consent is given or specific exceptions apply.

Unlike breath testing, blood test results are not immediate and may take days or weeks to process.

What Happens If You Refuse Chemical Testing?

After a lawful DUI arrest, refusal to submit to a breath test can result in administrative license suspension under Washington law.

  • First refusal: 1-year license suspension
  • Second refusal within 7 years: 2-year suspension
  • Third refusal: 3-year suspension

Refusal may also be admissible as evidence in court.

Administrative license suspension is separate from the criminal DUI case.

Why Sobriety Testing Matters

Sobriety test results often form the core of the State's evidence in DUI cases. However, these tests must be administered correctly and in compliance with statutory and scientific requirements.

Video evidence, calibration records, observation periods, and officer training all become critical in evaluating the reliability of the results.

Seattle DUI Defense Representation

Whether you submitted to testing or refused, DUI charges can be challenged through careful legal review of the stop, arrest procedures, and testing compliance.

If you have been arrested for DUI in Seattle, prompt legal evaluation is essential to protect your driving privileges and defense options.