Causes of False Positives on a Breathalyzer Test

Breathalyzer tests play a major role in most Texas DWI cases. Law enforcement officers often use breathalyzer tests during traffic stops and after arrests to determine a driver's blood alcohol content. If charged with DWI, prosecutors will almost certainly try to use those results to "prove" that the accused was intoxicated, especially when the test shows that their blood alcohol concentration (BAC) was over the legal limit of 0.08%.

What most people don't realize is this: breathalyzer tests are not perfect, and it's more common than you might think for a false positive breathalyzer test to occur. Many things can affect the accuracy of a breathalyzer test, and in some cases, there can be false positives or a result that is not the actual blood alcohol level that a person has.

DWI cases can be very complicated, and a false breathalyzer reading can make it worse. Understanding the causes of false positives on a breathalyzer test is important, especially if you are facing DWI charges in Texas.

How Breathalyzer Tests Work

A breathalyzer test estimates the blood alcohol concentration in a person's body by analyzing the alcohol molecules in a person's breath. It measures the alcohol present in a person's deep lung air, and then uses a formula to estimate the BAC.

It's common for law enforcement and prosecutors to use breathalyzer test results to justify an arrest and charges, but there are many things that can affect breathalyzer results and cause an incorrect reading.

Here are some of the most common causes:

Mouth Alcohol Contamination

One of the most common causes for inaccurate readings on a breathalyzer test is because there is alcohol in a person's mouth. These devices are meant to test the deep lung air, but not the alcohol in the mouth. If there are alcohol vapors in the mouth during the test, the machine can show false readings that might not be accurate.

Several things may cause residual mouth alcohol including:

• Recent drinking

• Burping

• Acid reflux

• Vomiting

• Use of mouthwash

• Certain medications

Even a small amount of alcohol residue in the mouth may affect the test result significantly.

Acid Reflux and GERD Can Cause False Positive Breathalyzer Test Results

Medical issues like gastroesophageal reflux disease (GERD) or acid reflux may also cause false positive breathalyzer readings.

Acid reflux may cause stomach contents and alcohol vapors to travel up into the mouth and throat. This can introduce mouth alcohol, which can elevate the BAC reading. Those who have the following conditions are more at risk of a false positive breathalyzer test:

• GERD

• Chronic acid reflux

• Heartburn

• Hiatal hernias

Police officers are not medical experts, and they may not notice these conditions during a DWI investigation.

Improper Observation Periods Can Cause Inaccurate Readings

Texas law enforcement officials are typically expected to observe a suspect for a period of time before administering a breath test. This is a time to make sure that the driver doesn't burp, vomit, eat, drink, smoke, or place other objects into their mouth.

If the officer doesn't do this, there could be contamination that can affect the breath test results.

Certain Foods and Drinks Can Cause False Positive Breathalyzer Readings

Some food and non-alcoholic drinks may cause false positive breathalyzer results, too. Products that contain alcohol or those that are fermented may temporarily leave alcohol traces in the mouth. Examples of these include:

• Kombucha

• Certain desserts

• Fermented foods

• Energy drinks

• Alcohol-based sauces

These substances don't cause actual intoxication, they could potentially affect a breath test if they were consumed shortly before testing.

Mouthwash and Breath Spray May Cause False Positive Breathalyzer Results

Many breath sprays and mouthwashes contain alcohol. Using these products before taking a breath test could leave residual alcohol in the mouth and cause the BAC readings to be higher.

Some of the products that can have this affect include:

• Mouthwash

• Breath spray

• Oral gels

• Dental products

If testing occurs too soon afterward, false positive results may occur.

Diabetes and Ketosis Can Raise BAC Readings

Those who have certain medical conditions, like diabetes, may also test positive on a breathalyzer test because their bodies might produce ketones or other chemicals that mimic alcohol.

Those who follow fasting regimens, are on keto diets, or those doing low-carb diets may also enter ketosis, which pushes the body to make more acetone, and this can be a false positive on a breath test.

Medications and Other Substances That May Affect Breath Tests

Certain medications and other substances may also cause false positive readings.

Examples include:

• Cough syrups

• Cold medications

• Asthma inhalers

• Oral pain medications

• Alcohol-based medicines

Some medications contain alcohol and others might affect metabolism or interfere with the testing process. Drivers can consume things capable of affecting the breath test results and never even realize it.

Calibration Problems and Lack of Proper Maintenance

The devices used to test blood alcohol concentration need to be maintained and calibrated. If they aren't, inaccuracies might occur.

Potential maintenance problems include:

• Sensor deterioration

• Software malfunctions

• Improper calibration

• Mechanical failures

Even small calibration errors may affect BAC readings and have serious legal consequences for those who test positive.

Defense attorneys often review maintenance and inspection records carefully during DWI cases to see if the device has been properly maintained.

Environmental Interference Can Affect Breath Tests, Too

Certain environmental substances may interfere with breathalyzer devices.

Some machines may react to airborne chemicals or vapors, including:

• Paint fumes

• Gasoline vapors

• Cleaning products

• Industrial chemicals

Drivers working in certain industries may be exposed to substances that potentially affect breath testing.

Although modern devices are designed to minimize interference, environmental contamination may still create reliability concerns in some situations.

Human Error During Testing

Breath testing procedures involve human operators, and mistakes can happen.

Common operator errors may include:

• Improper observation

• Incorrect machine operation

• Failure to follow testing procedures

• Inadequate training

• Recording errors

Even if the machine itself functions correctly, operator mistakes may affect the validity of the results.

Radio Frequency Interference

Some breath testing devices may be affected by radio frequency interference from nearby electronics.

Potential sources include:

• Police radios

• Cell phones

• Electronic equipment

Although safeguards exist, radio frequency interference has been raised as an issue in some DWI cases involving questionable breath test results.

Rising Blood Alcohol Levels

Breathalyzer results may also become misleading because of rising blood alcohol levels.

Alcohol takes time to absorb into the bloodstream fully. A driver may have consumed alcohol shortly before driving but still been below the legal limit while operating the vehicle.

By the time testing occurs later, BAC levels may have risen above 0.08%.

This creates situations where:

• The driver was legal while driving

• The breath test later shows an illegal BAC

Timing therefore becomes extremely important in some DWI cases.

Residual Alcohol After Dental Work

Certain dental appliances or recent dental work may trap alcohol in the mouth temporarily.

Examples may include:

• Dentures

• Braces

• Retainers

• Oral surgical devices

Residual alcohol trapped around these devices may contribute to inaccurate breath readings under certain conditions.

Breathalyzer Results Are Not Automatically Conclusive

Many people assume breathalyzer results are scientifically flawless. However, breath testing is only one piece of evidence in a DWI case.

Prosecutors may also rely on:

• Officer observations

• Field sobriety tests

• Driving behavior

• Dashcam footage

• Body camera recordings

Similarly, the defense may challenge the reliability of the breath test itself.

A high BAC reading does not automatically guarantee a conviction.

Challenging False Positive Breath Tests

A top-rated criminal defense attorney in Fort Worth may investigate several issues when challenging a questionable breath test result.

Possible defenses may involve:

• Medical conditions

• Improper observation periods

• Calibration failures

• Operator mistakes

• Mouth alcohol contamination

• Rising BAC arguments

Expert witnesses may also review testing procedures and scientific evidence.

Because breath testing technology has limitations, careful review of the evidence is often important. A horizontal gaze nystagmus defense lawyer in Texas can explain the impacts.

Penalties for DWI Convictions in Texas

There are significant consequences for those facing DUI charges in Texas. These include jail time, significant fines, losing driving privileges, higher insurance rates, ignition interlock requirements, and more. Because the penalties can be high, it's important to get a criminal defense attorney quickly to challenge breathalyzer results.

Contact a Texas DWI Defense Lawyer - Sparks Law Firm

Breathalyzer tests are not always accurate, and there are several things that can lead to false positives. Medical history or medical conditions, improper testing procedures, poor maintenance, calibration issues, mouth alcohol contamination, and human error can all play a part in the reliability of these tests.

Drivers who are accused of DWI should understand that even if they failed the breathalyzer test, that doesn't automatically mean that they are guilty. A DWI lawyer should look at all the circumstances surrounding the test to see if there are weaknesses in the prosecutors case. They have insight on dashcam and body camera footage in DWI cases in Texas.

Sparks Law Firm is a law firm in Fort Worth that helps those who are facing DWI charges. The legal team can take a look at the breath test evidence, investigate any potential errors, and work to protect the accused person's rights.

Those who are facing DWI charges should reach out to Sparks Law Firm to find out more about the legal implications of a DWI and how the firm can help. Free consultations are available.