A Colorado blood result of five nanograms or more of delta-9 THC per milliliter does not create the same automatic offense as a .08 alcohol result. Colorado law permits an inference that the driver was under the influence of drugs, but the inference can be challenged with other competent evidence.
The defense question is not whether THC appeared in the blood. It is whether the prosecution can prove that drugs made the person substantially incapable of safely operating a vehicle at the relevant time.
A Denver DUI attorney can compare the toxicology number with the driving, roadside observations, body-camera footage, and collection timeline.
Five Nanograms Creates an Inference, Not DUI Per Se
Under Colorado Revised Statutes section 42-4-1301, a whole-blood result of at least five nanograms of delta-9 THC permits an inference that the driver was under the influence of one or more drugs.
The statute also allows other competent evidence bearing on impairment. That language matters. A jury may consider the number, but the defense may present evidence that the person’s conduct did not match the state’s impairment theory.
By contrast, Colorado separately defines DUI per se through a BAC of .08 or more within the statutory period. Treating five nanograms as “the marijuana .08” erases that distinction.
Body-Camera Evidence Can Test the Impairment Claim
The defense should examine how the driver actually appeared and functioned. Clear speech, appropriate answers, normal movement, divided attention, and safe conduct shown on video can conflict with an officer’s conclusion.
The useful review is concrete:
- Did the vehicle movement show unsafe driving or only a technical violation?
- Did the driver understand instructions?
- Was speech slurred, delayed, or normal?
- Did balance problems appear consistently or only during an awkward test?
- Did the officer record red eyes or odor without explaining why those observations proved present impairment?
- Does the report omit behavior visible on video?
No single favorable moment decides the case. The complete sequence can rebut the claim that the laboratory number tells the whole story.
The Collection Timeline Deserves Separate Review
The blood draw occurs after the driving. Counsel should establish the stop time, arrest time, warrant or consent sequence, collection time, and laboratory receipt.
This article does not offer a universal conversion formula between a later THC result and an earlier degree of impairment. THC pharmacology varies, and a result should not be reverse-engineered through guesswork.
The defensible approach is to use qualified toxicology evidence when necessary and connect any opinion to the actual sample, timing, reported use, and observed conduct.
Higher Results and Mixed Substances Change the Argument
A higher THC concentration can be more difficult to explain. The legal inference remains rebuttable, but the practical burden of persuasion can increase as the reported concentration rises.
Alcohol combined with THC can also give the prosecution a different narrative than THC alone. Colorado’s DUI definition covers impairment from alcohol, one or more drugs, or a combination. A BAC below .08 therefore does not end a mixed-substance case.
The defense must address all alleged substances rather than isolating the most favorable number.
Field Tests Do Not Measure THC Concentration
Roadside maneuvers may be used as observational evidence, but they do not determine the number of nanograms in a driver’s blood. Performance can also be affected by instructions, surface, footwear, weather, injury, fatigue, or anxiety.
Counsel should compare the officer’s conclusions with the actual video and test conditions. A report that says “failed” may compress a more complicated performance.
A Useful Defense Connects the Number to the Person
The strongest review combines toxicology with behavior. Preserve medical information relevant to balance or eye observations, identify witnesses who saw the person close to the driving time, and obtain the complete video and laboratory file.
Do not create a new explanation in texts or social media. Statements about when, what, or how much was consumed can be used against the driver and may be scientifically inaccurate.
Challenge the Inference With the Full Record
A THC number can look conclusive even when the video, behavior, and collection timeline tell a more complicated story. Prager Law can compare the statutory inference with the full record and the prosecution’s burden of proof. If a THC blood result is driving your case, call 303-483-4452 or contact Prager Law.
