Breathalyzer Inaccuracies: All You Need To Know

Since the 1980s, every state across the U.S. has instituted tough laws against drinking and driving to create safer roads. These laws are having the desired effect. In 1985, according to the National Highway Traffic Safety Administration (NHTSA) in 1985, 41% of crash fatalities were alcohol-related, while in 2020, they made up about 30%. 

Since the pandemic, the pendulum has begun to swing the other way, and the United States has seen an uptick in drinking and driving accidents. Forty-nine states and the District of Columbia consider a blood alcohol content (BAC)  of 0.08% g/dL or higher impaired. Utah has a stricter policy, with a BAC of 0.05% g/dL as exceeding the legal limit of alcohol to drive. 

With drunk driving accidents in the U.S. occurring every 90 seconds and leaving 926 people injured daily, there is still work to do. Whether the stricter legal limits are to thank for the decrease in drunk driving accidents over the past decades is unclear, as there are other contributing factors too. What we do know is that the breathalyzer is here to stay, inaccuracies and all. 

The Blue Light in Your Rearview Mirror

Perhaps you are driving home from dinner, and you glance in your rearview mirror only to see the blue light of law enforcement flashing, signaling that you should pull over. Thinking of the beer or two you had with your pizza causes concern that you could be over the legal limit for alcohol consumption while driving. The officer will most likely offer you a chance to blow into the breathalyzer. 

What’s a Breathalyzer? 

A breathalyzer is a device used to estimate a motorist’s blood alcohol content (BAC) from a breath sample. In theory, the amount of alcohol in the bloodstream can be detected by the concentration of alcohol vapor measured in the driver’s breath. But can it be trusted? 

Just How Accurate are Breathalyzer Results? 

Spot on. Absolute accuracy. 

At least, that is what law enforcement officers and prosecutors would like you to believe. But that would be pretty misleading if we were being honest. In actuality, breathalyzers are accurate about 40% of the time. Additionally, the device has a margin of error in BAC readings of 0.005% and 0.02%. 

What Does This Mean for You? 

If we consider those facts about the breathalyzer test, it is quite possible that you may get a false positive reading that leads to driving under the influence (DUI) charges for you. DUI is a crime that can have a tremendous impact on every facet of your life. 

The accuracy of a breathalyzer machine depends on it being properly calibrated. Law enforcement must calibrate their devices based on how often they are used and the period of time since the last calibration. If you are arrested and charged with driving under the influence, your criminal defense attorney will probably consider challenging the accuracy of your breathalyzer reading. 

The device’s software must also be regularly updated to provide correct readings. If the police officer cannot testify to calibrating the breathalyzer appropriately and updating its software as necessary, your results may be thrown out.

False Positives That May Indicate an Illegal BAC

If you know that you have not been drinking and the breathalyzer still registers a false positive, you are probably wondering why that happened. There are several things that may have caused the incorrect results. Listed below are some of the more common things that may trigger an erroneous reading: 

  • Low-carb diets, like Keto or Atkins, while possibly helpful for weight loss, can put your body into a state known as ketosis. It causes your body to produce ketones and acetones. 
  • Fasting may produce the same effect and will result in a raised BAC reading.
  • Some medications can affect your breathalyzer results. Prescription drugs administered through an inhaler have compounds that behave similarly to the alcohol found in drinks, so they can register as an inflated BAC, even if you haven’t been drinking.
  • Gastrointestinal reflux disease and acid reflux can also cause a sufferer to register on a breathalyzer. The acids produced in the stomach or esophagus may cause the breathalyzer readings to be inaccurate. 
  • People with diabetes may also fail the breathalyzer test, even if they have not been drinking alcohol before blowing for the test. 

Environmental Results May Also Produce Inaccurate BAC Results

Environmental factors are another possible reason for an inaccurate breathalyzer test. For the test to be mistaken, these factors can be airborne rather than ingested. Here are some common environmental factors that may impact a breathalyzer test results: 

  • Paint fumes and solvents may register on a breathalyzer machine
  • Cleaning supplies that contain alcohol
  • Adhesives and plastics may contain chemicals that read as alcohol in a breathalyzer test
  • Leftover alcohol vapor from the last person tested on the device
  • Rubbing alcohol, even if it is on the skin, can alter the accuracy of the breathalyzer test
  • Contaminants on the mouthpiece
  • Particles that are in the air following an airbag being deployed
  • The battery in the breathalyzer and its freshness may cause accuracy issues.

Foods, Drinks, and Things Around the House That Might Trigger a False BAC Reading

Breathalyzers are very sensitive, but they are not particularly discerning. So, they may interpret some things as alcohol in the bloodstream that simply is not. Here are some of the foods that have triggered bad readings in other cases: 

  • Honey Buns or additional glazed cinnamon roll-type foods
  • Sugarless chewing gum
  • The yeast in bread and cakes has residual amounts of alcohol that can trigger a bad reading.
  • Protein bars
  • Hot sauce
  • Certain extracts
  • Foods cooked with alcohol, like rum cakes or vodka sauces

Non-alcoholic Beverages That May Cause a False BAC Reading

If you have not had an alcoholic beverage, you may think you can blow a breathalyzer without having an adverse reading. But, some other drinks may falsely raise your BAC in a breath test. Here are a few that may affect your results: 

  • Non-alcoholic beer
  • Non-alcoholic wine
  • Energy drinks
  • Fermented drinks like kombucha

Other Items That Might Pose a Risk

Most people would not consider the following items to put them at risk for an inaccurate breathalyzer test, but they have triggered false results before, so they are worth mentioning. 

  • Over-the-counter cough syrups, allergy medications, and sleep aids
  • Vitamins
  • Mouthwash
  • Breath sprays and other breath fresheners
  • Cosmetics, aftershave, and ointments
  • Denture adhesives and creams

Breathalyzer results are not as straightforward as law enforcement would have us believe. If you have been charged with a DUI, you may want to consider all the factors that could have impacted your breath test results.

Challenging Breathalyzer Inaccuracies

Breathalyzers are helpful tools for keeping the roads safe, but they are not infallible. If you feel your results were in error, David Breston understands the specifics of breathalyzer technology and can answer any of your questions.