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Breath Test

Breath Test - Alcohol

Breathalyzer Defense

Learn about the different test and the technology behind them below.

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Police Breathalyzer Testing Device

Breath Test
  • The new, state-of-the-art breath testing machine is called the Draeger Alcotest 9510.
  • The Draeger uses two technologies to measure alcohol on the breath.
  • One of those technologies is the same infrared spectroscopy method used by the Datamaster.
  • The IR technology of the Draeger is, however, more sophisticated than that used by the Datamaster because an additional “filter” is used to try to flag the presence of other chemicals on the breath that might cause a false positive.
  • In addition, the Draeger uses a separate technology, an electrochemical fuel cell, to come up with a separate alcohol measurement.
  • Because the fuel cell is sensitive only to alcohols, there is less potential for chemicals other than alcohol to cause a false-positive result.

Breathalyzer Accuracy - Machine Defense

Watch Linda M. Callahan Explain Potential Problems with Breath Testing Machines

Can breathalyzers be wrong?

  • Physiological differences between people in the population, such as lung capacity and breathing pattern, to name a few, will cause natural variations in the accuracy and reliability of breath test results.
  • It is also vital to the accuracy of the test that the operator of the machine administers the breath test itself as well as the pre-test mouth check and “observation period” correctly. 

Unlike Washington State Patrol breath test technicians, who maintain and repair Washington breath test machines, breath test operators (law enforcement officers) do not have in-depth training on how the machines work.

  • Most law enforcement officers around the state are certified to operate machines in their area. But their ignorance of the science involved and their relative inexperience in breath testing can cause mistakes during the test administration process.
  • These mistakes may seriously compromise the value of the results of the test.

What can affect a breathalyzer test?

  • The breath test machine may mistake certain chemicals on a person’s breath for alcohol.
  • The device is not designed to distinguish any interfering chemicals from alcohol, other than acetone.
  • However, it only recognizes a large amount of acetone on the breath.
  • Thus, a person’s reported breath test result may contain as much as 0.01 of acetone.

In a case where the breath test is 0.09 or under, this means the person may be innocent and wrongly convicted of DUI!

  • Acetone is one of the most common chemicals found on human breath.
  • If you believe that your breath test machine results were affected by a chemical, seek the assistance of Callahan Law, P.S., Inc.
  • We launch an in-depth investigation for clients who believe their test was affected by an interfering chemical.

“Tough DUI Laws Require Tough DUI Lawyers”

Linda M. Callahan

DUI Case Results

**Updated 08/03/2023**

DUI's Reduced
9 0 %
DUI's Dismissed
DUI's > Neg 1
DUI's > Reckless Driving
DOL Hearings Won

What can affect a breathalyzer test?

chemical defense


  • Because acetone is so common, the breath test machines are designed to detect it and adjust the result accordingly.
  • However, acetone may still account for the amount of the breath test below .01.
  • For example, if your breath test result was .08 and you had acetone on your breath, acetone may make up for .009 of the result, making the actual value well below .08.

Other chemicals that can be reported as alcohol

Chemicals that a person might be exposed to could account for a much higher portion of a breath test result without the machine detecting that the chemical is not alcohol.

Some chemicals may even account for an entire breath test result because breath test machines cannot distinguish them from alcohol at any level.

These chemicals include:

A solvent that you have absorbed through your skin or by breathing vapors from the chemicals may be to blame for a false positive breath test result.

It is essential to talk to an experienced Washington DUI attorney if you were arrested for DUI, and you have are often exposed to solvents.

We Author the DUI Manual Defense Attorneys rely on everyday for DUI Defense Strategies.

Contact us today for a 100% Free Consultation

Breathalyzer Accuracy - Acid Reflux and GERD

Breath Testing Errors that occur from GERD and Acid Reflux

Breath Testing Machine Errors

Acid Reflux | GERD Defense

  • Anyone who suffers from Acid Reflux or Gastroesophageal Reflux Disease ( or GERD) and takes a breath test after consuming alcohol may get a result that is much higher than the true alcohol level in the blood and/or lungs.
  • Acid reflux causes anything in a person’s stomach to rise from the stomach and into the mouth, including vapors containing alcohol molecules.
  • If a person has alcohol in their stomach and reflux pushes some of the alcohol or vapors into the throat or mouth, the vapor or alcohol coming from the stomach will substantially and falsely increase the alcohol concentration reported by the “breath” test machine, which is supposed to measure lung contents, not stomach contents.

Breath Tests & Acid Reflux

  • Washington law requires officers to observe the person for 15 minutes prior to the breath test to ensure no foreign substance is placed in the mouth.
  • Studies have shown that any alcohol in the mouth will evaporate within this 15-minute period.
  • Clearly, regurgitation of alcohol into the mouth would make the test inaccurate.
  • The officer is not likely to be able to observe this regurgitation even while watching the person closely.
  • The reflux regurgitation of alcohol is a silent, continuous flow of ethanol molecules from the stomach into the mouth – there need not be an obvious burp, belch or vomiting.
  • Studies show people who “reflux” stomach alcohol on breath tests, even tests administered hours after the consumption of alcohol, give artificially high breath test results compared to their actual blood alcohol level, as shown by blood analysis done at the same time.
  • Zantac, a medication designed to control reflux, can further exacerbate problems with the test by prolonging the time that alcohol remains in a person’s system.
  • However, do not expect the police and prosecutor to be compassionate to the special situation of those who suffer from acid reflux; in fact, most will blindly and obstinately argue that reflux cannot affect the accuracy of a breath test.

plan of action

know your rights

A person accused of driving under the influence who suspects reflux interference with their breath test should obtain medical records proving they have previously been diagnosed with the disease. In addition, they need the services of a knowledgeable DUI defense attorney who can effectively present the acid reflux defense in negotiation with the prosecution or at trial to a jury or judge. Our Washington DUI attorneys can provide you with the tough and well-versed legal representation you need and deserve. Let us put our more than 30 combined years of experience to work for you.

We Challenge The Following Evidence On Every Case.


Probable Cause

Before you were asked to step out of your vehicle, the officer has been gathering evidence to support the arrest.


Field Sobriety Tests

As Ms. Callahan likes to call them “Bad Science”, FST’s are virtually impossible to pass, especially if the officer is the one grading you.


Breath Test - BAC

Factory trained, Linda M. Callahan understands the science behind breath testing most attorneys don’t.


Blood Test

With extensive training at Axion Labs in Chicago, Linda M. Callahan has the relevant experience to challenge Blood test evidence.

Snohomish County DUI Attorney

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