How Field Sobriety and Breath Tests Work in a Washington DUI Stop
Getting pulled over for suspected DUI is stressful—and confusing. You might be unsure what’s happening, what your rights are, and whether you're making the right decisions. Field sobriety and breath tests play a major role in Washington DUI investigations, but many people don’t know what to expect until it's too late.
This post breaks down the process so you can better understand what these tests involve and what they mean for your case.
The DUI Traffic Stop: What Officers Are Looking For
A DUI stop usually begins with an officer noticing signs of impaired driving—swerving, speeding, or even something as small as a broken tail light. Once you're pulled over, the officer will observe your behavior. Slurred speech, the smell of alcohol, or fumbling for documents can all lead them to investigate further.
At this point, the officer may ask you to step out of the vehicle and perform a series of field sobriety tests (FSTs)designed to detect signs of impairment.
Understanding Field Sobriety Tests
Field sobriety tests are standardized physical and cognitive exercises approved by the National Highway Traffic Safety Administration (NHTSA).
The three most common are:
Horizontal Gaze Nystagmus (HGN): Following a moving object (usually a pen) with your eyes. Officers look for involuntary eye jerking that may indicate intoxication.
Walk and Turn: Walking heel-to-toe in a straight line, turning, and returning the same way. This tests balance, coordination, and your ability to follow instructions.
One-Leg Stand: Standing on one foot while counting aloud.
These tests can be difficult even for sober individuals—especially if you're nervous, tired, or dealing with a medical condition. It’s also worth noting: you are not legally required to perform field sobriety tests in Washington.
Portable Breath Tests at the Roadside
In addition to FSTs, the officer may ask you to take a portable breath test (PBT) using a handheld device. This is not the official breath test, but it can give officers probable cause to arrest you.
Important: You can refuse the PBT without license penalties. However, this refusal could still influence the officer’s decision to arrest you. The real legal consequences come into play later with the Evidentiary Breath Test at the police station.
The Station Breath Test: What You Need to Know
If you're arrested, you’ll be taken to the station for an official breath test using a DataMaster machine. Refusing this test can lead to a license suspension of at least one year under Washington’s Implied Consent Law.
Unlike the PBT, this test is admissible in court. That’s why officers must follow strict procedures, including a 15-minute observation period before testing. If protocol isn’t followed, an experienced Seattle DUI attorney may be able to challenge the results.
We Can Help
At Verity Criminal Defense, we understand the high stakes of DUI charges. Whether it’s challenging a breath test result or questioning the legality of a traffic stop, our firm is ready to fight for your rights. Learn more about our DUI defense services in Seattle and how we can help.