Most people assume a breathalyzer result is ironclad. If the machine says .10, you're guilty. End of story. That's not how it works. Breath test results can and do get challenged in court, and there are legitimate, well-recognized reasons why those results may not accurately reflect your actual blood alcohol content.
Here's what you should know if you've been charged with DUI in Yakima or Kittitas County.
How Breathalyzers Work (and Where They Can Go Wrong)
Breathalyzers measure alcohol in your breath and use that reading to estimate the alcohol in your blood. That word (estimate) matters. The conversion relies on a fixed partition ratio (2100:1), which assumes a standard relationship between breath alcohol and blood alcohol. But that ratio varies from person to person. Some people naturally have a higher ratio, which means the breathalyzer overestimates their BAC.
Beyond the science, there are several practical failure points:
Calibration and maintenance. Washington uses the DataMaster DMT breath testing machine. These machines must be regularly inspected, calibrated, and maintained according to strict protocols. If the machine was out of calibration or hadn't been properly serviced, the results can be challenged.
Operator certification. The officer administering the test must be trained and certified to operate the machine. If they weren't, or if their certification had lapsed, that's a problem for the prosecution.
The 15-minute observation period. Before a breath test, officers are required to observe you for at least 15 minutes to ensure you don't eat, drink, belch, or regurgitate - anything that could introduce mouth alcohol and skew the result. If that observation wasn't done properly, the test result can be questioned.
Medical conditions. GERD, acid reflux, and other gastrointestinal conditions can cause alcohol from the stomach to be present in the mouth and throat, leading to an artificially elevated reading. Dental work, certain diets, and even some medical conditions can affect results.
Environmental factors. Certain chemicals, including paint fumes, cleaning products, and some work-related substances, can register on breath testing equipment.
What About Refusing the Test?
Washington has an implied consent law, which means by driving on Washington roads you've already agreed to submit to a breath test if lawfully arrested for DUI. Refusing comes with immediate consequences: a one-year license suspension and the refusal can be used against you at trial.
That said, a refusal doesn't automatically mean a conviction. And sometimes, with the right defense strategy, a case without a breath test result can actually be harder for prosecutors to prove.
Every Case Is Different
There's no one-size-fits-all answer for how to handle breath test evidence. The value of a good DUI defense attorney is knowing which angles are worth pursuing in your specific case, and fighting hard on the ones that are.
If you were arrested for DUI in Yakima or Kittitas County and there's a breath test result in your case, I'd be happy to take a look. Free consultations: (509) 293-7593.
Tony Swartz is a DUI defense attorney in Ellensburg, WA, serving Yakima and Kittitas Counties.