Does Mouthwash Cause False Breathalyzer Results?

How Alcohol-Based Mouthwash Can Trigger DUI Arrests and What a Florida DUI Defense Lawyer Can Do to Fight It

If you were arrested for DUI in Florida and told the officer you hadn’t had anything to drink, only to blow over the legal limit on a breath test, you’re not alone. One of the most overlooked causes of a false breathalyzer result is something many people use daily—mouthwash. Alcohol-based mouthwashes can temporarily elevate the amount of alcohol detected on your breath, even when you’re stone-cold sober.

I’ve defended clients across Florida accused of DUI who were shocked to see a high BAC reading after using something as common as Listerine. The truth is, some breathalyzer results cannot be trusted, and it’s my job to expose the flaws in that evidence. Breath testing is not infallible, and if mouthwash contributed to a false positive in your case, you need someone who can prove it.

Let’s talk about how this happens, why the science matters, and how private legal representation can turn the case in your favor.

How Mouthwash Can Cause a False BAC Reading

Many popular mouthwashes contain a high percentage of alcohol. For example, Listerine contains approximately 26.9 percent alcohol by volume. That’s more than most beers and wines. The problem occurs when someone uses mouthwash shortly before a breath test. The alcohol in the mouthwash doesn’t go into your bloodstream—it coats the tissues in your mouth and throat.

Breathalyzer machines, like the Intoxilyzer 8000 used in Florida, are designed to measure alcohol from deep lung air, not from the mouth. However, when residual alcohol from mouthwash is present, it can interfere with the machine’s ability to make an accurate reading.

This phenomenon is known as “mouth alcohol contamination.” Breath machines can’t always distinguish between alcohol in your breath and alcohol in your mouth. If the officer administers the breath test too soon after you used mouthwash, the reading can be significantly higher than your actual blood alcohol concentration.

This is why Florida law enforcement is trained to observe a mandatory 20-minute waiting period before conducting a breath test. During this period, officers are supposed to ensure you don’t eat, drink, regurgitate, or place anything in your mouth. But if that observation period is not followed correctly, and you had recently used mouthwash, it could result in an invalid test.

Florida DUI Law and Breath Testing Protocol

Under Florida Statute § 316.193, it is unlawful to drive with a blood or breath alcohol level of 0.08 or higher. The statute reads:

“A person is guilty of the offense of driving under the influence… if the person is driving or in actual physical control of a vehicle… and the person has a blood-alcohol level of 0.08 or more grams of alcohol per 100 milliliters of blood or a breath-alcohol level of 0.08 or more grams of alcohol per 210 liters of breath.”

However, Florida Administrative Code Rule 11D-8.007 sets out the procedures that law enforcement must follow when conducting a breath test. It requires:

• A 20-minute observation period

• Use of approved breath test instruments

• Proper documentation and calibration of the machine

If the officer fails to follow these procedures exactly, the breath test result can be challenged in court.

Why Private Legal Counsel Makes a Difference in These Cases

When breath test evidence is at the center of a DUI charge, your defense often depends on technical details—calibration records, machine maintenance logs, observation period logs, and even the officer’s own dashcam or bodycam footage. Public defenders are often overwhelmed and under-resourced. They may not have the time to subpoena calibration records or challenge scientific evidence.

When I represent a client charged with DUI based on a breath test, I immediately request all records related to the machine used, the officer’s training history, and whether the required observation period was properly completed. I bring in toxicologists who understand how mouth alcohol can spike a breath test and whether the test was scientifically reliable.

Real Case Example: DUI Dropped After Mouthwash Defense

I once represented a client in Hillsborough County who was pulled over for a broken taillight. He had not been drinking but had just used a strong mouthwash minutes before being stopped. The officer noted a “strong odor of alcohol,” which was likely the mouthwash itself. My client consented to a breath test and blew a 0.10, just above the legal limit.

We obtained the bodycam footage and confirmed that the officer conducted the breath test only five minutes after the stop—far short of the 20-minute observation period required by law. My client had also informed the officer about the mouthwash, which was not noted in the report. We brought in a forensic expert who testified that alcohol-based mouthwash can produce residual alcohol readings that disappear within 10 to 15 minutes.

The state’s breath test technician admitted under cross-examination that mouth alcohol could contaminate the result if proper waiting periods aren’t followed. The prosecutor dropped the DUI charge before trial, and my client avoided a criminal conviction.

That outcome would not have happened without a private attorney digging into every detail of the case.

Legal Defenses to a False Breathalyzer Result From Mouthwash

These are some of the defenses I’ve used to challenge DUI charges tied to false-positive breathalyzer results:

Mouth Alcohol Contamination
We argue that the breath test reading was not a true measure of deep lung alcohol but was instead caused by mouthwash residue. Scientific studies and expert testimony support this claim.

Failure to Follow Observation Period
If the officer didn’t observe you for the full 20 minutes before the test, the result may be invalid. We use bodycam, dispatch records, and time logs to prove this failure.

Improper Machine Calibration or Maintenance
Breath test results are only admissible if the machine was properly maintained and calibrated. If the records show issues with the machine, we move to suppress the test results entirely.

Lack of Probable Cause for Arrest
If the only sign of impairment was the odor of alcohol and the breath test was flawed, the entire arrest may lack probable cause. We file motions to dismiss based on this argument.

Violation of Due Process
If the state failed to preserve video evidence or failed to provide breath machine maintenance records, we may argue a due process violation that can result in suppression or dismissal.

The Role of Scientific Evidence

Prosecutors often assume breathalyzer results are bulletproof. They’re not. Breath machines are sensitive to a range of factors—mouthwash, acid reflux, diabetes, even paint fumes. That’s why I work with independent toxicologists who can explain to a judge or jury how residual alcohol can cause a spike in results.

Florida courts have recognized the possibility of false positives due to mouth alcohol. Scientific literature, including studies published in peer-reviewed journals, confirms this. But you need someone who knows how to bring that science into your case and make it count.

Why You Need an Attorney Immediately

Once you’re charged with DUI in Florida, the clock starts ticking. You only have 10 days to request a formal review hearing to contest the administrative suspension of your license. Waiting too long can mean you lose that chance.

If you used mouthwash shortly before your arrest and believe it may have affected the breath test, you need to act fast. The sooner I get involved, the more evidence I can preserve and examine. Breath test machines are backed by government agencies, but they’re only as accurate as the people using them.

Fighting a DUI case based on a mouthwash defense requires attention to detail, scientific knowledge, and relentless advocacy. It’s not something to leave in the hands of an overworked public defender or to try handling on your own.

Musca Law, P.A. has a team of experienced criminal defense attorneys dedicated to defending people charged with a criminal or traffic offense. We are available 24/7/365 at 1-888-484-5057 for your FREE consultation. We have 30 office locations in Florida and serve all counties in Florida.

DUI Frequently Asked Questions (FAQs)

Can mouthwash really affect a breathalyzer reading?
Yes. Many mouthwashes contain high levels of alcohol that can linger in your mouth and throat. When a breathalyzer is administered too soon after using mouthwash, it may detect alcohol that is not actually in your bloodstream, resulting in a falsely elevated reading.

How long does mouthwash affect breathalyzer results?
Generally, the effect of mouthwash on a breathalyzer lasts less than 15 minutes. That’s why officers are required to observe you for at least 20 minutes before conducting a breath test. If that observation period is shortened or skipped, your result may not be valid.

Is mouthwash use a legal defense in DUI cases?
Yes. If we can show that your high breath test result was caused by mouthwash and not actual impairment, we can move to suppress that result. The defense focuses on proving the presence of residual mouth alcohol and exposing failures in the test procedure.

What should I do if I used mouthwash before a DUI arrest?
Tell your lawyer immediately. Let them know the brand and when you used it. That information helps us investigate whether the breath test result may be invalid due to mouth alcohol contamination.

Does Florida law allow breath tests to be challenged?
Absolutely. Under Florida DUI law and administrative code, breath tests must follow strict procedures. If the machine wasn’t calibrated correctly or the officer didn’t follow the rules, we can challenge the result and may get it thrown out.

Can a false breathalyzer result lead to a conviction?
Yes, if it goes unchallenged. Many DUI convictions are based on breath test results alone. That’s why you need a defense attorney who can question the science and expose the flaws that may have affected your case.

Will prosecutors drop charges based on a mouthwash defense?
They can. We’ve had cases dropped after demonstrating that the breath test was not scientifically reliable due to residual mouth alcohol. Each case is different, but when we present credible scientific evidence and procedural violations, prosecutors often reconsider their position.

How do I prove the officer didn’t observe me properly?
We use time-stamped video footage, police logs, dispatch records, and testimony to establish how much time passed before your test. If the officer failed to follow the required waiting period, it could result in suppression of the breath test.

What if I already admitted to using mouthwash?
That may actually help your case. Your admission shows honesty and gives us a clear explanation for the test result. We can use that fact to support our defense and show that you were not impaired.

Should I fight a DUI even if my BAC was over 0.08?
Yes. A number on a breath test isn’t the whole story. There are many ways to challenge the result, especially if it may have been caused by something like mouthwash. We’ve won cases with BACs over the legal limit because the test itself was flawed.

Musca Law 24/7/365 at 1-888-484-5057 For Your FREE Consultation

Musca Law, P.A. has a team of experienced criminal defense attorneys dedicated to defending people charged with a criminal or traffic offense. We are available 24/7/365 at 1-888-484-5057 for your FREE consultation. We have 30 office locations in Florida and serve all counties in Florida.