NC DWI Law Basics
North Carolina’s DWI statute, G.S. 20-138.1, creates one crime called “impaired driving” that the State can prove three different ways: by showing you were appreciably impaired, by showing an alcohol concentration of 0.08 or more at any relevant time after driving, or by showing any amount of a Schedule I controlled substance in your blood or urine. Understanding which prong the State is relying on is the first step in understanding your case.
When people talk about the NC DWI statute 20-138.1, they usually mean a short, dense section of Chapter 20 of the North Carolina General Statutes. It is only a few sentences long, but nearly every DWI trial in North Carolina is a fight over the meaning of one of its phrases: “drives,” “vehicle,” “public vehicular area,” “impairing substance,” “relevant time after the driving.” This guide walks through the statute line by line, explains the definitions it borrows from G.S. 20-4.01, and shows how North Carolina’s appellate courts have read each piece. If you are new to the subject, our North Carolina DWI guide gives the big picture first.
What does G.S. 20-138.1 actually say?
G.S. 20-138.1 makes it a crime to drive any vehicle on a highway, street or public vehicular area in North Carolina while impaired in one of three defined ways. Subsection (a) defines the offense, (a1) lets a driver use his own blood test as rebuttal, (b) says a legal right to use a drug is no defense, (b1) preserves challenges to chemical-test admissibility, (c) explains how the charge is pleaded, (d) makes it a misdemeanor sentenced under G.S. 20-179, and (e) excludes horses from the definition of “vehicle.”
A person commits the offense of impaired driving if he drives any vehicle upon any highway, any street, or any public vehicular area within this State: (1) while under the influence of an impairing substance; or (2) after having consumed sufficient alcohol that he has, at any relevant time after the driving, an alcohol concentration of 0.08 or more; or (3) with any amount of a Schedule I controlled substance, as listed in G.S. 90-89, or its metabolites in his blood or urine. (Close paraphrase; read the official text.)
Read the statute on ncleg.gov ↗Notice the structure. Every prong shares three common elements: (1) the person drove, (2) a vehicle, (3) on a highway, street or public vehicular area. Only the fourth element, the impairment element, changes. That is why defense lawyers analyze every DWI in two layers: first the “driving” layer (was this person driving, in a vehicle, in a covered place?), then the “impairment” layer (which of the three prongs can the State actually prove, and with what evidence?).
The pattern jury instruction used in North Carolina trials, N.C.P.I.—Crim. 270.20A, tracks this exactly. The jury must find, beyond a reasonable doubt, that the defendant was driving a vehicle, on a highway, street or public vehicular area, and that at the time he was impaired under at least one of the prongs the evidence supports.
One offense, three ways to prove it
North Carolina treats impaired driving as a single offense, not three separate crimes, so jurors do not have to agree on which prong was proven as long as they all agree the defendant is guilty. The North Carolina Supreme Court settled this in State v. Oliver (1996), holding that a disjunctive instruction on “under the influence” or “0.08 or more” did not produce a non-unanimous verdict.
This has real consequences. Prosecutors routinely charge and argue both (a)(1) and (a)(2) together. If a breath result is strong, the State leans on the number; if the number is suppressed or close to the line, the State falls back on the officer’s observations. A defense that knocks out only one prong may not win the case. The practical lesson: a good defense review looks at every prong the State could use, not just the one printed on a test ticket. Our checklist on how to review North Carolina DWI evidence is built around that idea.
What the State must show: your physical or mental faculties, or both, were appreciably impaired by an impairing substance (alcohol, drugs, or a combination).
Typical evidence: driving behavior, odor, speech, balance, field sobriety tests, admissions, drug recognition evaluations, and any chemical result.
No number required. A conviction is possible with no test at all, or with a test below 0.08.
What the State must show: an alcohol concentration of 0.08 or more at any relevant time after the driving, measured in breath (grams per 210 liters) or blood (grams per 100 milliliters).
Typical evidence: an Intox EC/IR II breath result or a blood analysis, plus proof the test was performed under G.S. 20-139.1.
No impairment required. A driver who seems fine can still violate (a)(2).
What the State must show: any amount of a Schedule I controlled substance listed in G.S. 90-89, or its metabolites, in your blood or urine.
Typical evidence: a laboratory toxicology report.
No impairment and no minimum level required. Note that marijuana is not Schedule I in North Carolina, so THC cases are prosecuted under (a)(1).
Prong (a)(1): “Under the influence of an impairing substance”
Under (a)(1), the State must prove that an impairing substance appreciably impaired your physical or mental faculties, meaning the effect was large enough to be recognized and estimated. G.S. 20-4.01(48b) defines “under the influence of an impairing substance” as having physical or mental faculties, or both, “appreciably impaired by an impairing substance.”
“Impairing substance” is defined broadly in G.S. 20-4.01(14a): alcohol, a controlled substance under Chapter 90, any other drug or psychoactive substance capable of impairing a person’s physical or mental faculties, or any combination. That covers beer and bourbon, but also prescription sleep aids, opioids, muscle relaxants, inhalants and THC products. Our articles on prescription medication DWI and marijuana and THC DWI go deeper on the drug side.
What does “appreciably” mean? The leading explanation comes from State v. Harrington (N.C. Ct. App. 1985). The court explained that consuming alcohol, standing alone, does not make a person impaired; a slight effect on the faculties is not enough; and the smell of alcohol alone does not control. On the other hand, the State does not have to prove the person was “drunk.” The effect must be appreciable, which the court described as sufficient to be recognized and estimated. The pattern jury instruction offers the same definition on request.
Because (a)(1) has no numeric threshold, it is the most fact-driven prong. The State usually builds it from three phases of the encounter: the vehicle in motion (weaving, speed, delayed reactions), personal contact (odor, speech, eyes, fumbling for documents), and pre-arrest screening (the standardized field sobriety tests, including HGN). Each phase has innocent explanations that a careful defense will develop: fatigue, injuries, nerves, footwear, weather, road surface, medical conditions, and the officer’s departure from training standards.
One more point people miss: a low breath or blood number does not end an (a)(1) case. Harrington noted that the State may prove DWI where the alcohol concentration is unknown or below the per se limit, citing an earlier case in which a conviction was affirmed with a 0.06 reading based on the officer’s opinion. A low number is strong defense evidence, but it is evidence, not an automatic acquittal.
Prong (a)(2): 0.08 “at any relevant time after the driving”
Under (a)(2), the State must prove an alcohol concentration of 0.08 or more at any relevant time after the driving, and a properly admitted chemical analysis is deemed sufficient evidence of that concentration. No proof of impairment is required. This is the “per se” prong.
Three definitions drive this prong. “Alcohol concentration,” under G.S. 20-4.01(1b), is grams of alcohol per 100 milliliters of blood or per 210 liters of breath, and results are reported to the hundredth, with anything between two hundredths rounded down. So a 0.089 is reported as 0.08, and a 0.079 is reported as 0.07. “Relevant time after the driving,” under G.S. 20-4.01(33a), means any time after driving in which the driver still has in his body alcohol consumed before or during the driving. And G.S. 20-139.1 controls how a chemical analysis must be performed to be admissible.
The “relevant time” language is what makes a test taken an hour after the stop legally meaningful. It also explains why the State does not need to “relate back” a breath result to the moment of driving: if the alcohol in your body at the time of the test was consumed before or during the drive, the test time is itself a relevant time. That is why drinking after driving (for example, at home before police arrive after a crash) is a genuine (a)(2) defense issue, because alcohol consumed after the driving does not count.
Defendants have argued that the statute’s “deemed sufficient evidence” language unconstitutionally presumes guilt. In State v. Narron (N.C. Ct. App. 2008), the court rejected that challenge, holding that the provision makes a properly admitted result prima facie evidence of alcohol concentration but does not presume any other element, such as driving. The jury may still reject the number. Attacking the reliability and admissibility of the result, through the breath-testing records, the observation period, the operator’s permit, or the blood chain of custody, remains the core of an (a)(2) defense.
Retrograde extrapolation is the flip side. When the test result is below 0.08, the State sometimes calls an expert to estimate what the concentration was earlier. In State v. Babich (N.C. Ct. App. 2017), the court held that an expert’s extrapolation from a 0.07 breath result should have been excluded under Evidence Rule 702 because it assumed, without supporting facts, that the driver had finished absorbing alcohol. The court found the error harmless on the other impairment evidence, which is itself a reminder that (a)(1) and (a)(2) travel together.
Prong (a)(3): Any amount of a Schedule I controlled substance
Under (a)(3), driving with any detectable amount of a Schedule I controlled substance or its metabolites in your blood or urine is impaired driving, even with no proof of impairment and no minimum level. It is the strictest prong, but also the narrowest.
Schedule I is defined by G.S. 90-89, North Carolina’s own list, not the federal schedule. As of November 2026 it includes, among others, heroin, MDMA, LSD, psilocybin and psilocin, many synthetic cannabinoids, and cathinones. It does not include marijuana or THC, which North Carolina places in Schedule VI. Common prescription drugs (oxycodone, alprazolam, zolpidem, amphetamine salts) are in other schedules. So (a)(3) rarely applies to a typical prescription or cannabis case; those are tried under (a)(1).
Because there is no impairment element, the defense in an (a)(3) case focuses almost entirely on the laboratory: whether the sample was lawfully obtained (see our summary of State v. Romano on warrantless blood draws), whether chain of custody is intact, whether the analyte identified is actually a Schedule I substance or metabolite under G.S. 90-89, and whether the analyst who performed the work is available to testify.
“Drives,” “vehicle” and “public vehicular area”: the elements every prong shares
No matter which prong the State uses, it must prove you drove a vehicle on a highway, street or public vehicular area, and each of those words has a statutory definition broader than most people expect.
- Driver / operator. G.S. 20-4.01(7) and (25) make “driver” and “operator” synonyms: a person in actual physical control of a vehicle that is in motion or has the engine running. Sitting behind the wheel of a running, parked car can be “driving.” See our parked-car case study.
- Vehicle. G.S. 20-4.01(49) covers any device that can carry people or property on a highway, except devices moved by human power. For Chapter 20, bicycles and electric-assisted bicycles count as vehicles. The DWI statute says “any vehicle,” not “motor vehicle,” which is why bicycles and riding lawnmowers can support a DWI charge.
- Highway / street. G.S. 20-4.01(13) and (46): the entire width of any way open to the public as a matter of right for vehicular travel.
- Public vehicular area. G.S. 20-4.01(32): areas the public uses for vehicular traffic, including parking lots of businesses, hospitals, schools and churches, beach areas used by vehicles, roads within or leading to subdivisions (gated or not), and private property an owner designates under G.S. 20-219.4.
Horses are the famous exception. In State v. Dellinger (N.C. Ct. App. 1985), the court held that a horse fit the broad definition of “vehicle” and that a rider with a 0.18 alcohol concentration could be convicted of DWI. The General Assembly responded in 1989 by adding subsection (e), which says that for G.S. 20-138.1, “vehicle” does not include a horse.
Subsections (a1), (b) and (b1): rebuttal, the “my prescription” myth, and admissibility
Subsection (b) says that being legally entitled to use alcohol or a drug is not a defense, so a valid prescription does not defeat a DWI charge if the drug appreciably impaired you. This is one of the most common misunderstandings we hear in consultations.
Subsection (b) does not mean a prescription is irrelevant. Lawful, as-directed use at a therapeutic dose is still powerful evidence on whether the drug actually caused appreciable impairment, and medical conditions treated by the medication may explain observations the officer attributed to impairment. But the legal question remains impairment, not permission.
Subsection (a1) gives a driver who submitted to a blood test under G.S. 20-139.1(d) the right to use that result to rebut evidence of a 0.08 or higher concentration. In practice, that matters when a driver asks for an independent blood test and the result is lower than the breath result. Subsection (b1) preserves the defense that a chemical analysis is inadmissible under G.S. 20-139.1(b2), the provision dealing with preventive maintenance records for breath-testing instruments.
Subsections (c), (d) and (e): pleading, punishment and the horse rule
A DWI charge is sufficient if it states the time and place and alleges impaired driving on a highway or public vehicular area; the offense is a misdemeanor, but punishment is set by a separate sentencing hearing under G.S. 20-179.
Under subsection (c), the charging document does not have to say which prong the State will rely on. That is why the citation you received probably just says you drove “while subject to an impairing substance.” You learn the State’s theory from discovery, the officer’s paperwork, and the chemical analysis.
Subsection (d) labels impaired driving a misdemeanor, but North Carolina’s DWI punishment scheme is unlike any other misdemeanor. After conviction, the judge (or, in superior court, the jury for contested aggravating factors) weighs grossly aggravating, aggravating and mitigating factors to place the case in one of six levels, from Level Five (24 hours to 60 days, fine up to $200) to Aggravated Level One (12 to 36 months, fine up to $10,000). Our sentencing levels guide and our new article on aggravating and mitigating factors cover that process.
- 1983The Safe Roads Act consolidates North Carolina’s older “driving under the influence” offenses into a single offense of “impaired driving” in G.S. 20-138.1, with alternative methods of proof.
- 1984The N.C. Supreme Court decides a group of cases on the new law, including State v. Shuping and State v. Coker, confirming the new structure.
- 1985State v. Dellinger holds that a horse is a “vehicle”; State v. Harrington explains “appreciable impairment.”
- 1989The General Assembly adds subsection (e): a horse is not a vehicle for G.S. 20-138.1.
- 1993A 1993 amendment (S.L. 1993-285) is reflected in the current per se limit of 0.08.
- 1996State v. Oliver: one offense; jurors need not agree on the prong.
- Dec. 1, 2006Current pattern jury instruction N.C.P.I.—Crim. 270.20A applies to offenses on or after this date.
The North Carolina cases that define G.S. 20-138.1
A handful of appellate decisions explain how each phrase of the NC DWI statute works in court; these are the ones a defense lawyer reaches for first.
Explained that the 1983 Act created one offense with alternative methods of proof without changing the basic meaning of “impaired”; drinking alone, a slight effect, or odor alone is not enough, but the State need not prove drunkenness. Impairment must be appreciable, meaning sufficient to be recognized and estimated.
Read the opinion ↗G.S. 20-138.1 creates a single offense that may be proved by either theory; a disjunctive jury instruction on “under the influence” or “0.08 or more” does not create a non-unanimous verdict. The Court also held the pretrial civil revocation was remedial, not punishment, for double jeopardy purposes.
Read the opinion ↗Rejected a due process challenge to the (a)(2) language that chemical analysis results are “deemed sufficient evidence”; the provision makes a properly admitted result prima facie evidence of alcohol concentration but presumes no other element.
Read the opinion ↗Retrograde extrapolation from a 0.07 breath result was inadmissible under Rule 702 because the expert assumed, with no supporting facts, that the driver was in the elimination phase. The error was held harmless given other impairment evidence.
Read the opinion ↗Held a horse is a “vehicle” under the broad definition in G.S. 20-4.01(49), so an impaired rider could be convicted. The legislature later added G.S. 20-138.1(e) to exclude horses, but the reasoning still shows how broad “vehicle” is.
Read the opinion ↗Our library also has detailed write-ups of other decisions that shape DWI cases at the stop and arrest stages, including State v. Parisi on probable cause and State v. Godwin on HGN testimony.
How the statute shapes a defense strategy
A strong defense maps every piece of evidence onto the statute’s elements: driving, vehicle, place, and each impairment prong the State could argue. The weakest element usually becomes the center of the case.
- Identify the State’s theory
Get the citation, the officer’s affidavit and notes, the chemical analysis result, and any toxicology report. Is the case built on a number, on observations, on a lab result, or all three?
- Test the shared elements
Can the State prove who was driving? Was the engine running? Was the location a highway, street or public vehicular area under G.S. 20-4.01(32)?
- Attack the number, if there is one
Review the breath-test ticket, permit, observation period, instrument records, or blood chain of custody. Look for post-driving drinking and any independent test under (a1).
- Re-examine the observations
Compare the officer’s narrative to video. Look for innocent explanations and departures from NHTSA field-test standards.
- Decide resolution
Only after all of that can you weigh a negotiated outcome against trial. See our guide on deciding between a plea and a trial.
Hypothetical: A driver blows 0.09 on the Intox EC/IR II but performs well on every field test and drove normally. Can the State still prove DWI?
- No, because he was not impaired
- Yes, under (a)(2), because impairment is not an element of the 0.08 prong
- Only if he admits drinking
Prong (a)(2) requires only a concentration of 0.08 or more at a relevant time after driving. The defense would focus on the reliability and admissibility of the test.
Hypothetical: A driver with a valid prescription for a sleep aid is appreciably impaired by it. Is the prescription a defense?
- Yes, a prescription is a complete defense
- Yes, if the bottle is in the car
- No, G.S. 20-138.1(b) says legal entitlement is not a defense
Subsection (b) removes the legal-entitlement defense. The fight is over whether the drug actually caused appreciable impairment.
Hypothetical: A blood test shows THC and no other drug. Which prong can the State use?
- (a)(1), appreciable impairment
- (a)(3), because THC is Schedule I
- (a)(2), because of the blood result
Marijuana is Schedule VI in North Carolina, not Schedule I under G.S. 90-89, so the State must prove appreciable impairment.
Hypothetical: Someone rides a horse home from a party, impaired, on a public road. Is that DWI under G.S. 20-138.1?
- Yes, under State v. Dellinger
- No, subsection (e) excludes horses
- Only on a highway, not a street
Dellinger said yes in 1985, but the legislature added subsection (e) in 1989. Other laws may still apply.
Related impaired-driving statutes you should know
G.S. 20-138.1 is the main DWI statute, but North Carolina has several neighboring offenses with their own elements. Each one is covered in more depth elsewhere in our library.
| Statute | Offense | Key difference from 20-138.1 |
|---|---|---|
| G.S. 20-138.2 | Impaired driving in a commercial vehicle | Per se limit is 0.04 in a commercial motor vehicle. See CDL DWI. |
| G.S. 20-138.3 | Driving by person under 21 after consuming | Any alcohol or controlled substance in the body; a Class 2 misdemeanor, not a lesser-included offense of DWI. See under-21 consequences. |
| G.S. 20-138.5 | Habitual impaired driving | A felony built on prior DWI convictions. See habitual DWI. |
| G.S. 20-179 | Sentencing for impaired driving | Not an offense; the sentencing procedure and six levels. |
People often ask whether North Carolina has a separate “DUI” offense. It does not; “DWI” is the common name for G.S. 20-138.1. We explain the terminology in DWI vs. DUI in North Carolina and in our older overview of NC impaired-driving charge types.
What to do if you are charged under G.S. 20-138.1
Write down everything you remember, keep every piece of paper you were given, and get your evidence preserved early, because video and records can be overwritten or lost.
Your paperwork usually includes the citation, a revocation report for the 30-day civil revocation, and the chemical analysis result or a refusal affidavit. Note the times on each: the stop, the arrest, the arrival at the testing site, and the test. Those times matter for the “relevant time” analysis and for your rights under G.S. 20-16.2. Write down what you ate and drank, and when, and any medications or medical conditions. Do not post about the case online.
- Keep the citation, revocation paperwork and test ticket together
- Write a timeline: last drink, driving, stop, arrest, test
- List every medication and medical condition
- Note any witnesses, receipts or bar tabs
- Ask a lawyer about preserving dash and body camera video
- Read how to prepare for your DWI consultation
From our book
Charged with DWI in North Carolina?
Our book walks through G.S. 20-138.1 and the evidence used to prove each prong, from the roadside to the breath room to the courtroom, in plain English.
Frequently asked questions about the NC DWI statute
What is the NC DWI statute?
North Carolina’s DWI statute is G.S. 20-138.1, “Impaired driving.” It makes it a misdemeanor to drive any vehicle on a highway, street or public vehicular area while appreciably impaired, with an alcohol concentration of 0.08 or more at any relevant time after driving, or with any amount of a Schedule I controlled substance in the blood or urine. Punishment is set under G.S. 20-179.
Can I be convicted of DWI in North Carolina if I blew under 0.08?
Yes. The State can still try to prove appreciable impairment under G.S. 20-138.1(a)(1) using driving behavior, observations and field sobriety tests. A result below 0.08 is significant defense evidence, but it does not automatically end the case.
Is a prescription a defense to DWI in North Carolina?
No. G.S. 20-138.1(b) says being legally entitled to use alcohol or a drug is not a defense. The question is whether the drug appreciably impaired you, and lawful, as-directed use can still be relevant evidence on that question.
Can you get a DWI in a parking lot in North Carolina?
Yes, if the lot is a public vehicular area under G.S. 20-4.01(32), which includes parking lots of businesses, schools, hospitals and churches and roads in subdivisions. Purely private property that is not open to public vehicular traffic may not qualify.
Does the State have to say which prong it is using?
No. Under G.S. 20-138.1(c), the charge only needs to allege impaired driving at a time and place. In State v. Oliver (1996), the N.C. Supreme Court held that jurors need not agree on which prong was proven.
Adkins & Purkey, PLLC
Talk to a North Carolina DWI lawyer
We will walk through which prong of G.S. 20-138.1 the State is relying on and where the evidence is weakest. Offices in Huntersville (Lake Norman) and Locust (Stanly County), serving Charlotte, Mecklenburg, Iredell, Cabarrus, Stanly and courts across North Carolina.
General North Carolina legal information as of November 2026, not legal advice for any specific case. Reading this article does not create an attorney-client relationship. Attorney advertising.
