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What Can Cause a False Positive on a Breathalyzer Test?

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Most people are familiar with breathalyzer tests, even if they’ve never had to take one. A breathalyzer test is a device police officers use to estimate a driver’s blood alcohol content (BAC).

There are two types of breathalyzer tests. Police officers use portable breath tests (PBTs) in their patrol vehicles during DUI traffic stops. There are also larger, more accurate breathalyzer machines at the police station.

Typically, when an officer suspects someone is under the influence of alcohol, they will administer a PBT. If the PBT result indicates the driver is likely intoxicated, the officer usually arrests them.

Then, the officer transports them to the police station and performs another test on the more accurate breathalyzer. Police may also request a blood draw, depending on the circumstances.

While breathalyzers can, in some situations, return fairly accurate results, there are also some common problems that lead to breathalyzer false positives.

What Can Lead to a Breathalyzer False Positive?

When discussing what can cause a false positive breathalyzer test, there are a few important things to consider. First, breathalyzers do not actually measure a driver’s blood alcohol content.

State law prohibits people from driving under the influence of drugs or alcohol. In the case of alcohol, it is considered drunk driving to operate a vehicle with a blood alcohol content of .08% or greater.

Breathalyzer tests work by measuring the amount of alcohol in the exhaled air from a driver’s lungs. The machine then uses this data to estimate the driver’s blood alcohol content. Given this reality, there are a few issues that can cause breathalyzer false positives.


A breathalyzer is supposed to measure the amount of alcohol in the air exhaled from within your lungs. But your breath contains air from your mouth as well as your lungs.

Most of the time, the presence of alcohol on your breath is an indication that you consumed alcohol. But certain things can create a false positive breathalyzer reading because they increase the amount of alcohol that is present and lingering in the mouth.

If you recently took medications or consumed certain foods, your breath may indicate the presence of alcohol even if you have not had a drink. Or this lingering, residual mouth alcohol can falsely increase your BAC reading. The following foods and medications may cause a false positive breathalyzer result:

  • Nyquil and other cough medications;
  • Sugar-free gum;
  • Kombucha or other fermented beverages;
  • Ripe fruit;
  • Some types of bread; and
  • Energy drinks.

Also, those with dental work like crowns and bridges may experience even higher rates of false-positive tests. This is due to alcohol getting trapped in small crevices within the dental work. If the police asked you to take a breath test and you failed although you were not drinking, it may be due to a false positive related to residual mouth alcohol.


Breathalyzer devices are complex machines that require police officers to perform routine maintenance. If a breathalyzer is not properly maintained, it can provide inaccurate results.

While police departments train officers on how to calibrate breathalyzers, officers often forget to perform this routine maintenance and proper calibration of the device.

Suppressing Evidence After a Breathalyzer False Positive

Police officers must have probable cause before arresting you for a DUI offense. To establish probable cause, an officer can rely on a properly administered breath test in conjunction with their observations of intoxication.

However, if the breathalyzer results are later called into question, it may result in the suppression of evidence. In other words, if the breathalyzer provided a false positive, officers cannot rely on the result to establish probable cause.

This means that the breath test results, the officer’s observations of intoxication, and any physical evidence they recovered after your arrest may be inadmissible at trial.

If a court excludes evidence the prosecution needed to prove their case, they may have no choice but to withdraw the charges against you. An experienced Wyoming criminal defense attorney knows exactly when and how to present a motion to suppress evidence.

Are You Facing a Wyoming DUI Charge?

If police recently arrested and charged you with a Wyoming DUI, reach out to Cowboy Country Criminal Defense to schedule a free case evaluation. A DUI conviction can have a lasting impact on your life and may threaten everything you’ve worked so hard for.

Our Wyoming criminal defense attorneys aggressively defend the rights of clients facing all types of serious crimes, including drunk driving offenses. We command an in-depth understanding of the science behind breathalyzer tests and use this knowledge to keep false-positive tests from being used as evidence.

When you bring Cowboy Country Criminal Defense onto your legal team, you can rest assured that your case, your future, and your freedom are in good hands.

To learn more, and to schedule a free consultation with a Wyoming DUI lawyer, give us a call at 307-333-7884. You can also reach us through our online form, and one of our attorneys will be in touch.