Carolina Criminal & DUI Lawyer BlogNorth Carolina drivers who are suspected of impaired driving may undergo two main types of breath or alcohol tests: a preliminary 
screening at the roadside and an evidentiary test under the state’s implied consent laws. These procedures are guided by statutes like G.S. 20-16.2, which defines the expectations placed on a driver once probable cause is established. Although both tests relate to detecting alcohol, they serve different functions and carry different legal consequences.
This article explains the difference between a quick roadside test (like a PBT) and the more detailed evidentiary procedure (commonly an Intoximeter EC/IR II test), as well as the implications of refusing to cooperate at either stage. If you want to discuss an implied consent issue or need guidance on a DWI charge Mecklenburg, Union or Iredell County NC, please call or TEXT the Powers Law Firm at 704-342-4357, or email Bill Powers at Bill@CarolinaAttorneys.com. A thorough understanding of North Carolina law can clarify how your case might proceed if you encounter allegations of driving while impaired.
Table of Contents: Breath Testing in North Carolina
- Introduction to Implied Consent in North Carolina
- Preliminary Screening Tests vs. Evidentiary Tests
- Legal Thresholds: Reasonable Suspicion vs. Probable Cause
- How Officers Administer an Evidentiary Breath Test
- Blood Testing: When Is It Used and Why?
- Refusing an Implied Consent Test: Consequences and Myths
- Defense Strategies and Court Proceedings
- Powers Law Firm: Legal Counsel for DWI Charges
Introduction to Implied Consent in North Carolina
Under N.C.G.S. 20-16.2, motorists who drive on North Carolina roads are deemed to have “impliedly consented” to an evidentiary chemical analysis if an officer arrests or charges that person with an implied-consent offense, typically related to impaired driving. This concept means that once law enforcement has reasonable grounds to arrest—probable cause—the driver must submit to a breath or blood test (urine testing is also allowed in NC) or face additional licensing consequences for a willful refusal.
Implied-consent usually applies to offenses such as DWI, driving with an open container, or underage drinking and driving. If the officer believes a violation occurred based on the driver’s appearance, odor of alcohol, or actions during a roadside stop, the law grants the officer authority to request an evidentiary test. The law also details how a driver is informed about the test, potential license revocations, and the right to contact a witness or attorney before proceeding.
Implied-consent does not automatically apply to every roadside scenario. For instance, an officer who only suspects that a driver has consumed alcohol might first use a preliminary breath test (PBT) to decide if further investigation is warranted.
Preliminary Screening Tests vs. Evidentiary Tests
North Carolina allows officers to perform roadside screenings using a PBT, sometimes called a “handheld breathalyzer.” This device, while recognized under 10A NCAC 41B, is not the same as the machine used for a formal, evidentiary reading.
Preliminary Breath Tests: AlcoSensor Screening
A PBT at the roadside indicates the presence of alcohol, helping the officer decide whether to make an arrest. The numeric reading is generally not admissible in court to show an exact BAC. Instead, the officer might note that the device detected a positive reading alcohol. Requiring a PBT under G.S. 20-16.3 does not in itself constitute an arrest, nor does refusing it result in an immediate license revocation. Refusing a portable breath test is not deemed a Willful Refusal in North Carolina.
Evidentiary Tests
The officer may arrest the driver if they have probable cause. Thereafter, they can request an evidentiary test, such as the Intoximeter EC/IR II breath analyzer. This test is performed at a law enforcement facility. Its outcome may be used in court if the state follows implied-consent rules, including providing the driver with certain rights and a waiting period. A result of 0.08 or higher can bolster (strengthen) the prosecution’s case, proving impairment.
Legal Thresholds: Reasonable Suspicion vs. Probable Cause
An officer conducts field observations—driving behavior, odor of alcohol, red eyes, or slurred speech—and may also request the driver perform Standardized Field Sobriety Tests (SFSTs). The combination of these factors and perhaps a preliminary breath test reading can establish probable cause for DWI.
Reasonable Suspicion
This lower standard allows an officer to initiate a traffic stop and result in roadside screening with a PBT if there are reasonable grounds to believe the driver has committed an implied consent offense.
Probable Cause
A stronger standard required for arrest. Once an officer has probable cause, the implied-consent law comes into play under G.S. 20-16.2, permitting a formal breath, urine test, or blood test. Should the driver refuse without legal grounds, the law prescribes potential license revocation for 12 months.
How Officers Administer an Evidentiary Breath Test
After a DWI arrest, the officer usually transports the driver to a breath-testing station at either the local jail, intake facility, or law enforcement center. North Carolina’s implied-consent procedures establish these steps:
Chemical Analysis Rights
The officer must advise the driver of the right to call a witness or lawyer, as well as the consequences of refusing or failing the test.
Observation Period
A waiting period (often 15 minutes) is observed to minimize mouth-alcohol effects.
Testing on the Intoximeter EC/IR II
The driver exhales into a stationary (desktop) breath testing machine designed to measure alveolar breath. Its electrochemical and infrared sensors compute and confirm the accuracy of a BAC (breath alcohol concentration) number that is often printed on a 1/2 sheet of paper. DUI defense lawyers sometimes refer to that as the “test ticket.”
If a driver refuses, the officer notes a refusal, triggering a possible civil revocation of driving privileges. However, prosecutors can pursue the DWI charge based on other evidence, such as officer observations and SFST results under the appreciable impairment prong of the NC Impaired Driving law.
Blood Testing: When Is It Used and Why?
While breath testing is standard in most DWI cases, blood samples are taken in certain situations:
Accidents or Injuries
If a driver requires hospital treatment or cannot blow into a device, an officer may request a blood draw.
Suspected Drug Impairment
If alcohol does not appear to be the sole factor, an officer might seek a blood sample analyzed through gas chromatography–mass spectrometry (GC-MS) to detect drugs or other substances.
Refusals or Equipment Issues
If the driver refuses a breath test while unconscious officers may request medical personnel to secure a blood sample (as the law “implies” a conscious person would agree to provide a sample) or secure a search warrant for blood in appropriate circumstances.
Blood samples require a chain of custody, with authorized personnel drawing the blood and a lab completing the analysis. Though more detailed, blood testing may be challenged if protocols or storage practices go awry.
Refusing an Implied Consent Test: Consequences and Myths
A driver who is arrested for DWI under implied-consent laws and refuses a breath or blood test faces:
Civil Revocation
Refusal generally leads to an immediate 30 Day Civil Revocation and later 12-month revocation of driving privileges, independent of the criminal DWI charge outcome.
Possible Limited Privilege
In some scenarios, a driver may obtain a willful refusal limited driving privilege after a waiting period, subject to statute-based eligibility.
Impact on Trial
The refusal may be referenced as evidence that the driver was worried about the result, though the driver can offer other explanations for refusing. DWI defense lawyers sometimes call that a “negative inference.”
Misconceptions include believing refusal “erases” the charge or that no BAC reading means no conviction. North Carolina allows prosecutors to rely on officer testimony and other field evidence to pursue a DWI even without a formal test result. There is more than one way to prove impaired driving in North Carolina.
Defense Strategies and Court Proceedings
Defense counsel examining an implied-consent DWI looks for any departure from prescribed procedure:
– Was the driver properly advised of rights and penalties?
– Was there an uninterrupted observation period before testing?
– Did the officer document calibration logs or solution checks if the Intoximeter EC/IR II is questioned?
– For blood draws, is the chain of custody solid?
The state usually introduces the arresting officer’s account, the breath or blood test readings, and any supporting details. If certain safeguards were not observed (e.g., ignoring the driver’s right to contact a witness), or if the equipment was improperly maintained, the defense might be able to challenge or seek suppression of the test results in appropriate circumstances.
Powers Law Firm: Legal Counsel for DWI Charges
North Carolina’s implied-consent framework involves much more than a quick roadside test. When probable cause leads to an arrest, the officer transitions to a formal breath or blood analysis under G.S. 20-16.2. These results can significantly influence a DWI prosecution, although procedural errors, calibration oversights, or misunderstandings about refusal rights may affect how the case proceeds.
If you have questions about a DWI charge or if an implied-consent test result is in dispute, reach out to the Powers Law Firm. Call or TEXT 704-342-4357 or email Bill Powers at Bill@CarolinaAttorneys.com. Understanding the differences between preliminary and evidentiary tests—and how refusal impacts a driver’s license—can guide your defense strategy and legal decisions.