Breathalyzer tests are often seen as solid evidence in drunk driving cases, but their accuracy is far from perfect. While these machines are designed to estimate the amount of alcohol in your blood based on your breath, they don’t give an exact measurement. Instead, they make an educated guess. Let’s explore how they work, why their results aren’t always reliable, and some possible defenses against a failed breathalyzer test.

How Does a Breathalyzer Work?

When you drink alcohol, it travels through your body and gets absorbed into your blood through your stomach and intestines. As your blood circulates, some of the alcohol moves into your lungs, mixes with the air, and gets exhaled. Breathalyzers measure the alcohol in your breath and use a formula to estimate how much is in your blood.

This sounds straightforward, but there’s a problem. Breathalyzers don’t actually measure the alcohol in your blood. Instead, they rely on a calculation called the "partition ratio." This ratio assumes that the alcohol in your breath relates to the alcohol in your blood in a fixed way—specifically, that 2,100 milliliters of breath contain the same amount of alcohol as 1 milliliter of blood. But people’s bodies don’t all work the same way, and this ratio can vary a lot.

Why Do Breathalyzers Sometimes Get It Wrong?

One reason that a failed breathalyzer test can be inaccurate is that breathalyzers aren’t designed to measure alcohol alone.

Your breath contains hundreds of chemical compounds, and some of them can confuse the machine.
For example, people with certain health conditions, like diabetes, can have high levels of acetone in their breath, which can be mistaken for alcohol.

Environmental factors can also interfere. If you work around chemicals like paint, gasoline, or cleaning products, traces of those substances can stick around in your body and lead to falsely high readings. Even wearing a mask while working with chemicals doesn’t always eliminate the risk of contamination.

Another issue is the variability in people’s bodies. The partition ratio isn’t a one-size-fits-all calculation. Some people naturally have ratios that differ significantly from the standard, meaning their breath test results may overestimate or underestimate their actual blood alcohol concentration (BAC).

Room and body temperature can also throw off the results. A breathalyzer is sensitive to the temperature of the air around it and the person being tested. If you have a fever, your BAC reading could be higher because alcohol evaporates more quickly at higher body temperatures.

What About Other Factors?

A breathalyzer assumes that the air being tested comes from deep in your lungs, but that’s not always the case. If you’re nervous, you might breathe more shallowly, which could skew the results.
People with asthma or other breathing problems might not be able to provide a proper sample, leading to inaccurate readings.

Food, drinks, or even medications can also affect the results. Mouthwash, breath sprays, or anything containing alcohol can inflate your BAC reading. Acid reflux, vomiting, or having alcohol residue in your mouth can create similar problems.

Timing is another critical factor. It takes time for alcohol to be absorbed into your bloodstream after you drink it. If you’re stopped soon after drinking, your breath might smell like alcohol, but your BAC could still be rising. This means a test taken later might show a higher result than when you were driving.

Finally, breathalyzers are machines, and machines aren’t perfect. They need to be calibrated and maintained regularly, and human error during testing can lead to false readings.

What to Do After a Failed Breathalyzer Test?

A failed breathalyzer test can feel overwhelming, but it’s important to understand that failing the test doesn’t guarantee a conviction for driving while intoxicated (DWI). Breathalyzers are far from infallible, and the results can be influenced by many factors, including faulty calibration, improper use, or individual health conditions. This is where having an experienced DWI attorney can make all the difference.

At Reece & Reece, Attorneys at Law, we have a strong track record of defending drivers against DWI charges, including cases involving failed breathalyzer tests. Our team knows how to examine the details that others might overlook. For instance, we can investigate whether the device was properly maintained or if the officer administering the test followed protocol. We also consider medical conditions or environmental factors that could have led to an inaccurate result.

Having a skilled attorney is critical because the legal system is complicated, and DWI charges can have long-lasting consequences. Without proper legal representation, you may face hefty fines, license suspension, or even jail time based on evidence that may not hold up under scrutiny. Our firm is dedicated to challenging unreliable evidence and protecting your rights.

Have You Failed a Breathalyzer Test? Contact the Experienced DWI Attorneys at Reece & Reece

Challenging a failed breathalyzer requires extensive knowledge and experience. If you’ve been charged with driving while intoxicated, it’s best to have a knowledgeable attorney by your side who can contest the results and defend your rights. The Johnston County DWI defense attorneys at Reece & Reece, Attorneys at Law provide dedicated representation and compassionate advocacy for a variety of criminal and traffic-related offenses, including DWIs. Call (919) 300-1249 to schedule a consultation and learn how we can assist you today.