Can You Challenge the Results of a Breathalyzer Test in Washington?

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Can You Challenge a Breathalyzer Test in Tacoma, WA?

If you’re facing a DUI charge in Washington State, you may be reliving a few key moments over and over. You remember being pulled over. You remember taking a test—or refusing to. You remember the moment they said your blood alcohol concentration (BAC) was too high. And then, you remember being charged.

You’re not alone in thinking that a failed Breathalyzer test ends the story. But that’s not true. At Smith & White, PLLC, we regularly challenge DUI charges based on flaws in breath test results—because those tests aren’t always as reliable or straightforward as they appear. In fact, they can be wrong, and we’ve helped clients prove it.

Why the Breath Test Isn’t Always the Final Word

Washington’s legal limit for BAC is 0.08. If your test result is at or above that number, many people—even first-time defendants—assume the state has all it needs to convict you. But breath test evidence is not bulletproof. It is subject to strict protocols, mechanical limitations, and human error. And when those safeguards break down, the results can often be thrown out or successfully challenged in court.

Challenging the Breathalyzer: Common Legal Strategies

There are several legal and technical issues that may render a breath test unreliable. Our Tacoma DUI lawyers examine every step of the process, from the moment of your traffic stop to the handling of the machine itself.

1. Was the Breathalyzer Properly Maintained and Tested?

Washington State law requires breath testing machines to undergo regular quality assurance checks. If the machine used in your case was not properly calibrated or maintained, your test results may be invalid. For example:

Machines must pass annual testing and inspections.
Logs showing whether the device was functioning correctly are reviewable in court.
Some devices have known tendencies to skew high or low.

If you blew a borderline result (just above 0.08), and we discover the machine had a bias toward overestimation, your actual BAC may have been legal.

2. Was the 15-Minute Observation Period Followed?

Before administering a breath test, law enforcement must observe you continuously for 15 minutes. This rule ensures you don’t burp, vomit, chew gum, or ingest anything that could affect your breath sample.

If an officer walked away—even briefly—or allowed you to use the restroom, that 15-minute rule was violated. Most testing rooms are equipped with video. If you reach out quickly enough, our firm can work to preserve the footage and use it to suppress the test.

3. Was the Officer Certified to Administer the Test?

Every officer who gives a breath test must be certified and current on their training. If the officer’s certification was expired—or if they deviated from approved protocols—the results may be inadmissible. Police officers, like anyone else, can miss renewal deadlines. These details matter.

4. Was the Stop and Arrest Itself Legal?

Even if your BAC tested high, that evidence can be thrown out if the traffic stop or arrest was unlawful. For example:

Was there reasonable suspicion to pull you over?
Did the officer articulate valid cause to request a breath test?
Were you read your rights and properly advised?

Our Tacoma DUI lawyers will scrutinize every step. If your constitutional rights were violated, the breath test—and everything that followed—may be excluded from evidence.

5. Could Another Substance Have Affected the Results?

Breath tests aim to detect ethyl alcohol (ethanol), but they aren’t always that precise. They can misread other substances as alcohol, especially:

Acetone: Naturally occurs in people with diabetes or those on strict low-carb diets.
Isopropanol: Created during ketosis, a fat-burning state that produces alcohol-like compounds in the breath.

For example, painters, fuel technicians, and even those using alcohol-based hand sanitizers may inhale compounds that trigger false positives. These “interferents” can be detected in court through expert testimony or data from the device’s detection logs.

6. Was a Portable Breath Test (PBT) Used?

If you were given a breath test roadside, it likely involved a portable breath test device. These devices are not admissible in Washington court for proving guilt. They are used for investigative purposes only, and participation in a PBT is voluntary.

Many drivers don’t realize this distinction—and many officers fail to clearly explain it.

Realistic Case Example: Challenging the Breathalyzer in Pierce County

Let’s say a Tacoma man is pulled over late at night for allegedly swerving within his lane. The officer smells alcohol and requests a breath test at the station. The defendant blows a 0.09. He is charged with DUI.

Our firm reviews the machine’s records and discovers that it had not been tested within the required maintenance window. Additionally, bodycam footage shows the officer stepped out of view for over five minutes before the test.

We file a motion to suppress the test. With the key evidence excluded, the prosecution agrees to reduce the charge to reckless driving.

Refusing the Breath Test: What You Need to Know

If you refused to take a breath test, the legal analysis is different—but no less important. Refusals can lead to:

Automatic license suspension under Washington’s implied consent laws.
Increased penalties upon conviction.
Potential admissibility of your refusal at trial (under certain circumstances).

Still, refusals are not the same as guilty pleas. We’ve helped clients successfully fight refusal-based cases by challenging the legality of the stop, the validity of the warnings given, or the circumstances under which they declined.

Our Local Focus: Defense Across Tacoma and Surrounding Areas

Smith & White, PLLC is based in downtown Tacoma—just a block from the courthouse. Our attorneys have deep experience defending DUI charges in:

Pierce County (Tacoma, Puyallup, Lakewood)
Southern King County (Kent, Federal Way, Auburn)
Thurston County (Olympia)
Kitsap County (Port Orchard)

We’ve handled hundreds of DUI cases. And we know how to spot—and use—errors in the system.

Your Next Step: Get a Free DUI Case Analysis

If you’ve been arrested for DUI in Tacoma or anywhere nearby, don’t assume the Breathalyzer seals your fate. Every case is different. Every test is challengeable.

Facing DUI charges? Don’t navigate the system alone—reach out to our Tacoma office today for a free consultation.