Breathalyzer Tests – FAQ

Charlotte DWI Lawyer Brad Smith answers the question: “Are breath test results always accurate?”


Police commonly use breathalyzer tests to determine whether a driver is impaired. In North Carolina, the legal alcohol limit is 0.08% blood alcohol concentration (BAC). If you are found to have a BAC higher than 0.08% you could be arrested and charged with driving while impaired (DWI). It is helpful to understand breathalyzer tests so you know your rights if you get stopped by law enforcement.


wine-DWI-Charges-in-North-Carolina-Defense-Attorney-239x300What are Breathalyzer Tests?


A breathalyzer is a device that measures the blood alcohol concentration through the breath. There are two types of breath alcohol tests including a preliminary breath test, also called a portable breath test (PBT), and the chemical test. Law enforcement generally uses portable tests at vehicle stops as a way to generally determine possible impairment. A chemical breathalyzer test is completed at the police station and typically provides more accurate results. There are various machines the police use such as the Alco-Sensor, Intoxilyzer, the DataMaster, and others.


How Do Breathalyzer Tests Work?


Breath tests work by measuring the concentration of alcohol in your breath. When a person consumes alcohol, the body emits ethanol. Breathalyzer tests use various types of technology to detect the blood alcohol concentration. When you blow into the device, a sensor determines the amount of ethanol in your exhalation. The amount of alcohol in the bloodstream rises immediately after you take a drink and later begins to drop. If a test is completed at the incorrect time, it may not be accurate. Portable tests are often less accurate than other types of tests.


Can I Refuse a Breathalyzer Test?


North Carolina has an implied consent law that states drivers agree to a chemical test for alcohol when they obtain their driver’s license. The law specifically says that a driver must comply with a request from law enforcement to complete a chemical test for alcohol when the officer reasonably believes that person may be impaired. You can refuse a preliminary breath test, however, it won’t prevent an arrest.


What Happens if I Refuse a Breathalyzer Test?


If you refuse a chemical breath test (such as the one completed at the police station), you will likely face separate charges and penalties. The charges are civil, not criminal. You will face suspension of your driver’s license for at least a year, as well as fines and administrative fees. The penalties increase if you have had a prior DWI conviction. Further, the fact that you refused the test can be used against you in court. If you hold a commercial driver’s license, the penalties are more severe. If you refuse a test and have had a prior refusal, DWI conviction, or leaving the scene of an accident infraction, you may lose your license for 10 years.


Can I Challenge Breathalyzer Results in Court?


One of the best ways to fight DWI charges is to challenge the breathalyzer test. The law requires the police officer to provide you with your rights before you perform the test. If they fail to do so, it may be possible to exclude the results of the test in court. If the test was not performed properly or if the results were not evaluated adequately, you might be able to prove that the test was inaccurate.


The testing device itself must be in good working order and properly calibrated and maintained or it might not provide correct data. The person administering the test must have adequate training on how to use the device. If the test was administered at the incorrect time and therefore, may not reflect true impairment. You may also elect to obtain your own independent test so you may show that the results were different. This is especially helpful if you were close to the BAC limit.


A DWI conviction can negatively impact every area of your life for years to come. Therefore, you will want to vigorously defend DWI charges with help from an experienced attorney. Please contact us today to get a phone, video or in-person consultation by calling at (704) 370-2828 to speak with our detail-oriented and well-versed lawyers with offices in Charlotte, Lake Norman, and Monroe, please contact Arnold & Smith, PLLC today or find additional resources here.







The criminal defense attorneys at Arnold & Smith, PLLC make it their mission to zealously defend their clients on a wide range of criminal matters at both the state and federal levels. These matters may include any charge from traffic offenses; DWI/DUI; drug charges (from simple possession to possession with intent to distribute and trafficking); gun permit denials; weapons offenses; and property crimes (larceny, breaking and entering, robbery, fraud, embezzlement, white collar offenses); to sexually related offenses (indecent exposure; sexual assault, crimes against nature, removal from sex offender registry); and violent crimes (domestic violence; assault; manslaughter; homicide, murder). Other legal issues that Arnold & Smith, PLLC criminal clients may be facing include restraining orders, restraining order and probation violations, expungements; appeals; and immigration issues related to criminal charges. Our criminal defense attorneys are passionate about ensuring that individuals empower themselves by being informed about their constitutional rights, and stand at the ready to fight in the defense of those facing criminal charges.





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