Defenses to a Failed Breathalyzer Test in North Carolina

By Doug Edwards

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DUI/DWI Defense

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Last Modified on Jun 03, 2025

In a stop where you are suspected of driving while intoxicated (DWI) or driving under the influence (DUI), you will likely be asked to complete a breathalyzer test, either at the scene of the stop or later at the police station. If your results are over the legal limit, this can be used as evidence against you. It’s useful to understand the defenses to a failed breathalyzer test in North Carolina, such as challenging the device’s accuracy or how it was administered.

The Different Types of Breathalyzers

Breathalyzers measure the amount of alcohol in someone’s breath to estimate their blood alcohol concentration (BAC). There are two types of breathalyzers involved in a DUI traffic stop or arrest, and both are referred to as breathalyzers despite being different.

1. Roadside testing breathalyzers, or preliminary breath tests, are used by police officers during a traffic stop or at an accident scene to determine if a driver is under the influence. These are portable devices, and the results are frequently unreliable.
2. Breathalyzers administered at the police station are another type of chemical test. These are not portable, and the results are more reliable, but that doesn’t mean they are infallible.

If a breathalyzer test estimates a BAC over the legal limit, the officer will likely arrest you for a DUI. The results of the test can be used against you in your criminal case.

North Carolina has implied consent laws, meaning that by having a license and driving in the state, you agree to submit to a breathalyzer chemical test at the station. Refusal to do so can come with consequences, including the immediate suspension of your driver’s license.

Driving under the influence is taken very seriously. In 2023, the North Carolina Division of Motor Vehicles reported 12,146 alcohol-related vehicle crashes, out of 284,157 total crashes in the state. Although alcohol crashes only made up 4.3% of all crashes, they made up 7.0% of injuries and 22.4% of fatalities. If you are arrested on DWI charges, it is crucial that you get skilled legal support.

How Can a Breathalyzer Result Be Challenged?

It can be very stressful to be faced with a failed breathalyzer test. However, it is important to know that this doesn’t guarantee you will be convicted. When you hire a DUI lawyer, they can review the specifics of the device used, your own diet or medical conditions, and other details about your case. There may be several options for challenging the breathalyzer results.

Test Administration

The breathalyzer test at the traffic stop is administered by the officer, while the breathalyzer at the station must be administered by a qualified operator. Error by either of these parties can impact the test’s results. Other issues with the administration of the test include:

• Uncertified or insufficiently trained test administrators
• Unapproved breathalyzer device
• Failure to inform of your right to refuse the test
• Modifications of the device
• Failure to follow testing protocols or device instructions

Test Calibration or Maintenance

Breathalyzers need to be calibrated frequently to ensure accuracy. If they are not, this can affect the results. For breathalyzers in the station, there are regulations that require calibration on a set schedule. Often, forensic analysts are required to investigate the calibration of the machine to determine if it was accurate.

Machines that are poorly maintained can also result in inaccurate results. Maintenance for breathalyzers also has regulatory requirements. The maintenance logs of the machine can be reviewed to determine the frequency and quality of repairs. Insufficient records may also be used as proof of improper maintenance.

Test Environmental Factors

The results can also be inaccurate due to environmental factors, including:

• Medical conditions, such as diabetes
• Diets, such as keto or high-protein diets
• Use of mouthwash or other products containing alcohol
• Certain foods or drinks
• Medication, such as allergy medications
• Acid reflux or vomiting
• Residual alcohol

Hire a DUI Lawyer

In order to effectively challenge the results of a breathalyzer, it is crucial that you hire a skilled DUI attorney. They have the resources to investigate all of these possibilities and potentially be able to prevent the test from being used as evidence. This could prevent conviction or mitigate the severity of the consequences.

FAQs

What Is a Good Excuse for Failing a Breathalyzer Test?

There are several valid reasons for someone failing a breathalyzer test, even if they are not impaired or over the legal limit. Readings can be inaccurate because the breathalyzer device was improperly maintained or calibrated, or the officer administered the test improperly. Environmental factors can also influence the results of a breathalyzer, such as certain medications, mouthwash with alcohol in it, or even medical conditions.

An attorney can review your specific case to determine the right defense.

Can You Deny a Breathalyzer Test in North Carolina?

In North Carolina, you are allowed to deny a breathalyzer test, although some refusals can have legal penalties. For preliminary breathalyzers at the scene of an accident or a traffic stop, there should be no consequences for refusing. However, for breathalyzer tests at the police station, the state has an implied consent law. If you refuse this test, it will result in immediate license suspension. If you are convicted, the refusal will mean your penalties are more severe.

Is Refusing a Breathalyzer Worse Than a DUI?

If the breathalyzer is the breath chemical test, then refusing it will lead to immediate revocation of your license for 30 days. If you are convicted of a DUI, there may be an additional license suspension in your penalties. It can make a DUI conviction worse to refuse a breath test. If you take a breath test and blow under the legal limit, the results can be used as rebuttal evidence. It is often better to agree to a breathalyzer.

Are You Automatically Guilty If You Refuse a Breathalyzer?

No, you are not automatically guilty if you refuse a breathalyzer, although there are administrative penalties for refusing the test given at the station.

If there is no breathalyzer test, other evidence from the scene will be used, including the officer’s testimony. You could be convicted of a DUI if your driving was impaired by a substance, even if that substance wasn’t measured in a breathalyzer. If you are convicted, the breathalyzer refusal can increase some penalties.

Reach Out to Edwards Law, PLLC

If you failed a breathalyzer test, it is not the end of your case. There may still be options to avoid a DWI in North Carolina. Contact Edwards Law, PLLC, today.