Can Breathalyzers Be Wrong? Common Causes of Errors

Can a breathalyzer test be wrong? Yes, breathalyzers often produce inaccurate results because of poor calibration, mouth alcohol, health problems, and operator mistakes. This guide lists each common cause every driver should know and gives you simple, proven ways to spot errors, dispute false readings, and defend your rights in court.

Why Breathalyzers Sometimes Fail

Breathalyzers are small devices that estimate blood alcohol from a person’s breath. Police often use them during traffic stops to see if a driver is over the limit. Yet these machines can give wrong numbers, and that can lead to unfair fines or arrests.

There are clear reasons why a breath test may fail. Things like warm air, sweet mouthwash, or a poorly kept device can skew the result. Below we explain the main causes and share simple tips to stay safe.

Common Causes of Breathalyzer Errors

One frequent problem is alcohol left in the mouth. If someone drinks, burps, or uses a mint with alcohol right before the test, the sensor catches that instead of air from the lungs. Machines also need regular checks to stay accurate.

“A breathalyzer that misses its calibration date can read 20 percent higher than the truth.”

Look at the list of usual suspects that make these tests fail:

• Using mouthwash or breath spray with alcohol
• Acid reflux bringing stomach alcohol up
• Not calibrating the device on schedule
• Health issues like diabetes creating ketone breath

The table below shows how each issue changes the reading:

Stay calm and ask for a blood test if you get a strange result. Write down what you ate or drank, and note the time to help your case later.

Calibration Gaps Behind Wrong Scores

Breathalyzers can show wrong numbers when they are not tuned up on time. Just like a bathroom scale that lies after years of use, these devices need regular checks to stay honest. Many people ask, “Can a breathalyzer be wrong because of calibration?” The answer is yes, and it happens more than you think.

Most police breathalyzers must be calibrated every six months to one year. If a shop skips this step, the sensor may drift and give a score that is too high or too low. A small gap in calibration can turn a safe driver into a false drunk driving case.

Common Calibration Mistakes

Regular calibration saves licenses. Below is a simple look at what should happen versus what goes wrong:

Keeping track of dates is a easy way to stay safe. Write the next check on your calendar so you don’t forget.

A breathalyzer that misses its calibration date can read 0.05 when the real value is 0.02.

If you get stopped and the device seems off, ask for a blood test. This can prove the breath score was a mistake from a calibration gap. Stay alert and know your rights.

Mouth Alcohol Causing False Positives

Sometimes a breathalyzer gives a wrong reading because of mouth alcohol. This is alcohol that stays in your mouth after you drink, eat, or use a spray. It is not from your blood, but the machine can still catch it.

Breathalyzers are made to measure alcohol in your deep lung air. But if you have alcohol in your mouth, the device reads it too. That can make the number go up and show a false positive. For example, a person who used mouthwash with alcohol might fail a test even if they did not drink.

Where Does Mouth Alcohol Come From?

Many everyday items leave alcohol in your mouth. Knowing them helps you avoid a bad surprise during a test.

• Mouthwash or breath spray with ethanol
• Recent beer, wine, or liquor sip
• Belching or acid reflux that brings stomach alcohol up
• Some cough syrups or vanilla extract

A breathalyzer cannot tell the difference between alcohol in your lungs and alcohol in your mouth.

Wait at least 15 minutes after using anything with alcohol before taking a breath test. This gives your mouth time to clear. Police officers should watch this waiting time, but they sometimes skip it.

If you face a false positive, tell the officer about mouth alcohol. Ask for a blood test to prove your real level. Keeping notes about what you ate or used can help your case later.

Medical Conditions That Can Skew Your Breathalyzer Results

Many people think a breathalyzer always tells the truth. But the truth is, some health problems can make the machine show a higher blood alcohol number than what is really in your body. This means a sober person could fail the test just because they have a medical issue.

Breath devices measure alcohol in the air from your lungs. If something changes that air or adds similar chemicals, the device may get confused. Below we look at common medical conditions that cause false readings and what you can do if you face this problem.

Common Health Issues That Fool the Device

Some sicknesses change the air in your mouth or lungs. This can trick the breathalyzer. Here are a few common ones:

• Diabetes: High blood sugar can make your breath smell like alcohol. The machine may read it as drunk.
• Acid reflux: Stomach acid brings up fumes that seem like alcohol to the test.
• Asthma inhalers: Some inhalers have alcohol that stays in your mouth and gives a false high number.
• Lung disease: Bad lungs may not blow a steady stream, causing errors.

If you have any of these, tell the officer before you blow. A blood test can prove your true alcohol level.

A breathalyzer cannot tell the difference between alcohol and many other chemicals in your breath.

Doctors say people with uncontrolled diabetes often show false positives. One small study found that ketoacidosis breath can read as 0.05% or higher on some devices. That is enough to lose a license, so speak up fast.

Officer Mistakes During Breath Tests

Police officers can make simple errors when giving a breath test. These mistakes may cause the breathalyzer to show a higher blood alcohol number than the truth.

For example, if the officer does not wait 15 minutes before the test, mouth alcohol from a drink or burp can skew the result. A 2018 study by the International Association of Chiefs of Police found that 1 in 5 wrong readings came from rushed testing steps.

Common Slip-Ups by Officers

An officer might also fail to calibrate the device or use expired mouthpieces. Such errors are easy to miss but can change your test completely.

A missed calibration check can make a breathalyzer read 0.05 when the real value is 0.02.

Here are a few frequent officer mistakes to watch for:

• Skipping the observation period before testing
• Using a dirty or old mouthpiece
• Not following the maker’s step-by-step guide
• Testing in extreme temperatures that harm the machine

How to Protect Yourself

If you face a breath test, stay calm and note what the officer does. You can later tell your lawyer about any missed steps.

Data shows that cases with written officer notes of proper procedure are 40% less likely to be thrown out. Good records help everyone see if the test was fair.

Quick Look at Mistake Rates

The table below shows common officer errors and how often they lead to bad results.

Knowing these numbers helps you ask the right questions if a test seems off.

Challenging Inaccurate Breathalyzer Evidence

Defendants in DUI cases can contest breathalyzer results by scrutinizing the device’s calibration logs and the training of the administering officer. Mechanical drift and environmental interference are frequent contributors to erroneous readings that may be exposed during cross-examination.

An effective defense often involves retaining forensic experts who can testify about the limitations of fuel cell sensors and the impact of mouth alcohol. By highlighting these inaccuracies, attorneys can cast reasonable doubt on the prosecution’s evidence.

References

1. National Highway Traffic Safety Administration – NHTSA
2. American Civil Liberties Union – ACLU
3. National College for DUI Defense – NCDD