Impaired Driving and DUI Enforcement
This domain tests Colorado's impaired-driving statutes, the expressed consent process, and standardized field sobriety testing. Questions often hinge on one number, one time window, or the difference between two similar charges.
The charging options
- DUI - alcohol, drugs, or both impair the driver to the slightest degree, or BAC is 0.08 or more.
- DUI per se - BAC 0.08 or more within two hours of driving.
- DWAI - BAC of 0.05 to 0.079, or impairment less than DUI but enough to affect judgment.
- Under 21 - a measurable BAC of 0.02 or more supports an underage drinking-and-driving charge; the standard is effectively zero tolerance.
- Commercial drivers - 0.04 while operating a commercial vehicle.
- Marijuana: Colorado law allows a permissive inference of impairment at 5 ng/mL of delta-9 THC in whole blood. A fourth or subsequent DUI-related conviction can be charged as a felony.
Expressed consent
Any person operating a vehicle on Colorado roads has already consented to testing. Refusal triggers a license revocation - one year for a first refusal, longer with priors - and the refusal can be used against the driver at trial. Post-McNeely, a blood draw generally requires consent, a warrant, or a recognized exception; a mandatory blood draw is not automatic.
Field sobriety testing
Use the three validated NHTSA tests: horizontal gaze nystagmus (four clues per eye; the most discriminating), walk-and-turn (eight clues), and one-leg stand (four clues). These tests show impairment, not a precise BAC. A preliminary breath test supports probable cause; evidential testing follows arrest. Drug cases call for a Drug Recognition Expert evaluation.
Worked example
A driver is seen driving erratically at 12:25 a.m., stopped at 12:40 a.m., and gives a blood result of 0.09 at 1:10 a.m. Reasoning: the per se charge is satisfied because 0.09 exceeds 0.08 and the sample was taken within two hours of driving; DUI impairment is also supported by the driving behavior and test performance; DWAI is a lesser included offense, not an alternative when the result is 0.09.
Traps that cost marks
Thinking 0.08 is required for any DUI. Confusing DWAI with DUI. Ignoring the two-hour per se window. Forgetting that refusal carries its own revocation and can be mentioned at trial. Assuming a blood draw needs no warrant or consent. Treating HGN as a BAC estimator.