What Could Cause an Inaccurate Breathalyzer Reading?

Have you recently been arrested for DWI in Houston? Does a breath test show that you had alcohol in your system? Don't lose hope just yet. Breath tests are inherently unreliable. In fact, there is a margin of error of 50 percent when breath test results are compared to blood test results.

What can cause breath tests to be so vulnerable to inaccuracies? There are actually many different factors that can cause the results of a breathalyzer to be inaccurate. Proving that the results of your breath test aren't valid can be instrumental in your DWI defense. Without evidence to support its case, the state will be more inclined to offer a plea or drop the charges.

Problems With the Machine Itself

Breathalyzer test results can be inaccurate because of problems with the machine itself. At Doug Murphy Law Firm, P.C., our Houston DWI lawyers will thoroughly analyze the breathalyzer device that was used during your DWI stop. Finding issues with the machine can help to invalidate your breath test results.

Calibration and Maintenance

Texas state law requires breathalyzers to be calibrated on a regular basis. Calibration helps to make sure that each breathalyzer device is performing as designed. When a breathalyzer is not calibrated on a regular basis, as required by law, the results can be inaccurate.

Our attorneys will request the calibration records and notes for the particular machine that was used during your DWI stop. If we find that the breathalyzer has not been calibrated, or that the records show the device tends to be problematic, we will fight to have the results thrown out.


Breathalyzers are delicate pieces of scientific equipment. The sensors within the device can become damaged or destroyed if the breathalyzer is not stored properly. The ideal storage space for a breathalyzer is a cool and dark place. If police leave breathalyzer devices in hot vehicles or in direct sunlight, the accuracy of tests can be compromised.

Improper Use

Breathalyzers can only be accurate if the person using the device is properly trained. All police officers in Texas are required to receive formal training and education from the state. However, many officers forget much of what they learn over time. If the breathalyzer test is not administered correctly, the results cannot be trusted.

The Things You Consume Can Trigger a False Positive

Breathalyzer tests results can also be wrong even if the machine is working properly and administered by an officer who is properly trained. Many times, the things you consume can interfere with the results of a breath test. In some cases, the things you consume can trigger a false positive. This means that the machine recognizes alcohol in your system when none is present. Other times, the machine correctly recognizes alcohol in your system that is derived from innocent products. It is important to be very candid with your attorney about what you consumed before you were arrested for DWI. The more detail you can provide, the better your attorney can help you.


It's true, the food you eat can sometimes trigger a positive result on a breath test. Why? Many foods actually have trace amounts of alcohol. There are two primary reasons foods may contain alcohol. The first is when food is prepared using alcohol, such as wine, whiskey, or beer. The alcohol may be an ingredient in the food or used to prepare the food. The second is when food relies on the process of fermentation. Yeast breads, for example, which rise because of the fermentation process, are well-known for having residual alcohol. Foods that may contain trace amounts of alcohol include:

  • Very ripe fruit
  • Yeast breads
  • Protein bars
  • Honey Buns
  • Hot sauce
  • Vanilla extract
  • Kombucha
  • Vinegar
  • Lip balm
  • Energy drinks, and
  • Sugarfree gum.

Breathalyzer results that detect alcohol in your system because of something you have consumed are not technically inaccurate. There is actually alcohol in your system. However, the test is not sophisticated enough to identify the source of the alcohol. It can't tell that your BAC was .015 because you ate a Honey Bun, rather than having a few sips of beer. The officer will simply see that you have some alcohol in your system. The state has discretion about when it will file charges for DWI. If your attorney advocates on your behalf and can offer a valid explanation for why you would legitimately have trace amounts of alcohol in your system, you can avoid criminal charges.


Most mouthwashes on the market actually contain alcohol. If you use mouthwash to freshen your breath shortly before you drive, or even while you're in the car, you will have trace amounts of alcohol in your system. Mouthwash can be particularly problematic if police do not administer the breath test correctly.

Cold Remedies

Cold remedies, such as flu and allergy medicines, also contain small amounts of alcohol. Tell your attorney if you were battling a cold or allergies when you provided a sample of your breath for testing. A positive breathalyzer result could be triggered by cold medicine in your system.

Your Breath Can Throw Off Testing Results

There's a reason that police must receive intensive training before they can use a breathalyzer in the field. A breathalyzer is a scientific device. The person executing the test must follow specific directions and ensure that the best possible sample is used. However, this is not always the case. Many officers simply use whatever breath sample they can get, which is not always the most accurate representation of your blood alcohol concentration.

Shallow Breath

Breath tests should be conducted using a sample of your deep lung air. This requires you to take a very heavy breath and draw air from deep within your lungs. Scientists have established that this type of sample is the best reflection of your blood alcohol concentration. Things like mouthwash or chewing gum are much less likely to impact results using deep lung air. However, many police simply rely on a shallow breath sample. Why? It is easier to obtain and more likely to show an elevated BAC. Trace amounts of alcohol in the mouth can skew the accuracy of your test results.

Insufficient Sample

Breathalyzers work by analyzing a sample of your breath. In order to provide an accurate result, you must provide a certain volume of breath. If you cannot provide a sufficient sample the test will register an error. The test may not register the minimum volume of breath if you aren't properly instructed by the officer or if the machine itself is clogged.

Breathing Pattern

The way you breath can actually affect the results of your breath test. A study found that holding your breath, keeping your mouth closed, and shallow breathing can actually increase your BAC readings. An officer should keep these factors in mind when preparing you to take a breath test. You should be calm and breathing normally when providing a sample of your breath. If an officer does not make sure that you are prepared to provide the best sample, the result can be inaccurate.

Your Health Conditions May Jeopardize Breathalyzer Accuracy

Sometimes your own health conditions can cause breath test results to be inaccurate. There is very little you can do to prevent a skewed result. However, it has been well-established that certain conditions can affect breathalyzer results. Your attorney can offer evidence of your condition to undermine the validity of the results.


Breathalyzers can mistakenly identify acetone as alcohol. This can be problematic if you are diabetic. When you have diabetes you will have an elevated number of ketones in your blood. Elevated ketones actually increase acetone in your system and breath.


Do you suffer from asthma? If so, you'll want to let your attorney know. Many asthma medications, including albuterol and budesonide, have been known to affect the validity of breath test results. Using an inhaler before you drive could cause you to register a false positive on a breath test.

Acid Reflux

Acid reflux can be incredibly painful. It can be even more aggravating when the condition affects the accuracy of your breath test. When you suffer from acid reflux, the contents of your stomach make its way to your throat and mouth. If you've consumed alcohol or foods that contain trace amounts, that alcohol may be more prevalent when a test is administered due to this condition.

Get Help Fighting Inaccurate Breath tests in Houston

Have you been arrested on suspicion of DWI in Houston? Do breath test results show that you had alcohol in your system? Breath test results can be wildly inaccurate. You have the right to fight those results, and the attorneys at Doug Murphy Law Firm, P.C. can help. Call us today at (713) 229-8333 to schedule a free consultation.

Our experienced Houston DWI lawyers will review your case and determine the best strategy for your defense. As your attorneys, we will thoroughly investigate your breath test and search for the best ways to invalidate the results. Call us today to learn more.

Contact Us Today

If you are facing DWI or other criminal charges in Texas, contact our office today to discuss your case, so we can begin working on your defense. Please provide only your personal email and cell phone number so that we can immediately and confidentially communicate with you.