What C.R.S. 42-4-1301 Actually Prohibits
Colorado DUI laws are concentrated in one long section of the traffic code, C.R.S. 42-4-1301. People talk about "a DUI" as if it were one thing. The statute treats it as a family of related offenses, each with its own elements, and a single traffic stop can produce charges under several of them at once. Reading a complaint or summons gets much easier once you know which subsection does what.
The core offenses, in the order they appear in the statute:
- DUI, subsection (1)(a): driving a motor vehicle or vehicle while under the influence of alcohol, one or more drugs, or a combination.
- DWAI, subsection (1)(b): driving while ability impaired by alcohol, drugs, or both.
- Habitual user, subsection (1)(c): driving while a habitual user of a controlled substance, a less common charge.
- DUI per se, subsection (2)(a): driving with a BAC of 0.08 or more within two hours of driving.
- Underage drinking and driving (UDD), subsection (2)(a.5): a driver under 21 with a BAC from 0.02 through 0.05.
The same section also holds the evidence rules, in subsection (6), that tell a judge or jury what a test result is allowed to suggest. Those rules matter as much as the offense definitions, so they get their own section below.
| Offense | Where | What has to be proven | Usual classification (first time) |
|---|---|---|---|
| DUI | 42-4-1301(1)(a) | Substances left the driver substantially incapable of clear judgment, physical control or due care | Misdemeanor |
| DWAI | 42-4-1301(1)(b) | Substances affected the driver to the slightest degree, reducing the ability to drive safely | Misdemeanor (lower sentencing range) |
| DUI per se | 42-4-1301(2)(a) | BAC of 0.08 or more within two hours of driving | Misdemeanor |
| UDD | 42-4-1301(2)(a.5) | Driver under 21 with BAC from 0.02 to 0.05 | Traffic infraction |
"Substantially Incapable" Versus "Slightest Degree"
The difference between DUI and DWAI is a difference in degree, and the statute spells out both standards in its definitions. Under the influence means the substance has made the driver substantially incapable, mentally or physically, of exercising clear judgment, sufficient physical control or due care in the safe operation of a vehicle. Impaired means the driver was affected to the slightest degree, so that the person was less able than they ordinarily would have been to exercise that same judgment, control and care.
That gap explains how DWAI functions in practice. It is a lower bar for the prosecution, and it is also the charge that negotiated outcomes often land on, which is why so many people first meet the term when reading a plea offer. A DWAI is not a traffic ticket, though. It is a criminal conviction, and it counts as a prior offense if there is ever a second case.
Statute note
Neither definition mentions a number. DUI and DWAI are about the driver's condition; test results are evidence of that condition. Only the per se and UDD offenses are defined by a number.
The BAC Numbers and What Each One Triggers
Colorado measures alcohol concentration in grams per hundred milliliters of blood or grams per 210 liters of breath. Several lines appear across the statutes, and each does a different job. Our interactive BAC explorer on the home page shows them side by side.
- 0.05 or less. The evidence rules in C.R.S. 42-4-1301(6) point toward a finding that alcohol did not impair the driver. Other evidence, including drug evidence, can still be offered.
- More than 0.05 and less than 0.08. A permissible inference that the driver was impaired, which lines up with DWAI.
- 0.08 or more. The DUI per se offense if the result is within two hours of driving, plus an inference of being under the influence. It is also the line for an administrative revocation case at the DMV, explained in the Colorado DUI license revocation guide.
- 0.15 or more. One way to meet the statutory definition of a persistent drunk driver in C.R.S. 42-1-102, which brings interlock and alcohol education requirements on the licensing side.
- 0.02 (under 21) and 0.04 (commercial vehicles). Lower lines for specific drivers, covered below.
A "permissible inference" deserves a plain explanation. It means the fact-finder may conclude something from the number, not that it must. The defense can offer evidence that cuts the other way, such as testing problems or timing. How strong an inference is in a particular case is exactly the kind of question a licensed attorney is there for.
Reading a Charging Document
Summonses and complaints usually cite subsections rather than names. This matrix translates the most common ones. It is a reading aid, not a prediction of how any case will go.
Drivers Under 21 and Commercial Drivers
The 0.02 line for drivers under 21
UDD covers a driver under 21 whose BAC is at least 0.02 but not more than 0.05. It is a traffic infraction rather than a criminal offense, but it has its own license revocation track at the DMV. Once a young driver's result is above 0.05, the same DWAI and DUI provisions that apply to adults are in play as well.
The 0.04 line for commercial vehicles
Commercial drivers face a lower 0.04 line while operating a commercial motor vehicle, and commercial license disqualification rules (state and federal) can follow a DUI even when it happened in a personal car. A commercial license holder should raise those rules specifically with a lawyer, because they are separate from the ordinary penalties.
What Counts as "Driving"
The statute speaks of driving a "motor vehicle or vehicle." Colorado's traffic code defines vehicle broadly, and Colorado courts have read "drive" to reach situations where a person has actual physical control of a vehicle, not only motion on a road. Where that line falls (a parked car with the engine running, a bicycle, an electric scooter) depends heavily on facts. We flag it here because readers are often surprised by how far the words reach, not to suggest how any situation would be decided.
- One section, 42-4-1301, holds DUI, DWAI, per se, UDD and the evidence rules.
- DUI and DWAI are about the driver's condition; per se and UDD are about the number.
- 0.05, 0.08 and 0.15 each do a different job; 0.02 and 0.04 apply to specific drivers.
- A DWAI is a criminal conviction and counts as a prior in later cases.
Drug cases follow the same definitions with different evidence; the Colorado drug DUI and THC guide covers them. For sentencing ranges by offense, continue to the Colorado DUI penalties guide.
Verify Colorado amends its DUI statutes often. Check the current text of C.R.S. 42-4-1301 on the Colorado General Assembly site and ask a licensed Colorado attorney how it applies to you. Last reviewed November 2026.