Colorado police may build a drug DUI case using driving observations, statements, roadside testing, body-camera footage, a Drug Recognition Expert evaluation, and chemical test results. A blood test does not always establish that a driver was impaired at the time of driving, especially when marijuana or prescription medication is involved.
Hebets & McCallin P.C. reviews each stage of the investigation to determine whether the traffic stop was lawful, whether officers followed required procedures, and whether the evidence supports the charge. Summer concerts, festivals, sporting events, mountain trips, and holiday gatherings can lead to increased traffic enforcement in Denver, Colorado, and nearby communities.
Why Drug DUI Enforcement Increases Around Summer Events 
Colorado summers bring crowded event districts, outdoor concerts, brewery gatherings, camping trips, professional sporting events, and holiday travel. Roads near downtown Denver venues, Red Rocks, mountain corridors, and recreation areas may have heavier traffic and a larger police presence.
Officers may conduct impaired-driving patrols near event exits or along routes commonly used by attendees. Police do not need to see a driver use marijuana, prescription medication, or another drug before beginning an investigation. An officer may look for signs of impairment after observing driving behavior or speaking with the driver during a traffic stop.
Common reasons for a traffic stop include:
- Drifting within or outside a lane
• Driving well below the posted speed limit
• Braking late or stopping beyond a marked line
• Making an unusually wide turn
• Failing to respond promptly to a traffic signal
• Speeding or following another vehicle too closely
• Driving with a broken light or obscured license plate
A traffic violation does not prove drug impairment. It may give an officer a lawful basis to stop the vehicle and investigate further.
How Driving Observations Become Evidence
A Colorado drug DUI investigation often begins before the officer activates emergency lights. The officer may document the vehicle’s speed, lane position, braking, turning, and response to surrounding traffic. Those observations may later appear in the police report, body-camera narration, dash-camera footage, and courtroom testimony.
After the vehicle stops, the officer may note:
- How quickly the driver responds
• Where the vehicle comes to a stop
• Whether the driver has difficulty locating a license, registration, or proof of insurance
• The driver’s speech, eye appearance, movements, and attention
• Whether the driver understands and follows instructions
Summer conditions may affect those observations. A driver leaving a long outdoor event may be tired, dehydrated, sun-exposed, or distracted by traffic. Dust, allergies, contact lenses, and fatigue may affect eye appearance. Nervousness during a police encounter may affect speech, coordination, or memory.
These facts do not automatically defeat a charge. They may provide explanations for conduct that an officer interpreted as evidence of drug impairment.
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Questions About Marijuana, Medication, and Recent Use
During a traffic stop, an officer may ask where the driver has been, whether the driver consumed alcohol, and whether the driver used marijuana, prescription medication, or another substance. The officer may also ask when the substance was used, how much was taken, and whether the driver has a medical condition.
A statement such as “I used cannabis earlier today” may become an important part of the prosecution’s case. The timing of use matters because the presence of a drug or metabolite does not always establish that the substance impaired the driver at the time of driving.
Drivers should remain calm and should not physically resist an officer. A driver also has the right not to volunteer an explanation that may later be used as evidence.
Read more about police questioning and constitutional protections:
https://www.hebetsmccallin.com/searches-and-seizures-where-do-your-rights-end/
How Field Sobriety Tests Are Used in Drug DUI Cases
An officer may ask the driver to perform roadside maneuvers commonly associated with alcohol DUI investigations. These may include an eye examination, a walk-and-turn exercise, and a one-leg stand.
Officers may describe a driver’s performance as evidence of balance problems, divided-attention difficulty, or an inability to follow instructions. Drug impairment may be difficult to evaluate because different substances can produce different signs. Some substances may cause drowsiness. Others may cause agitation, rapid speech, muscle tension, or unusual eye movements.
Roadside testing may also be affected by:
- Uneven pavement, gravel, or a sloped shoulder
• Poor lighting
• Traffic noise and passing vehicles
• Heat, dehydration, or physical exhaustion
• Footwear or restrictive clothing
• Knee, back, balance, or neurological conditions
• Anxiety or confusion about the instructions
Body-camera footage may help the defense compare the officer’s written description with what occurred. A report may state that a driver swayed or failed to follow instructions, while the recording may show minor movement, unclear directions, or roadside conditions that made the exercise difficult.
Learn more about Denver DUID defense:
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How Drug Recognition Evaluations Are Used
When an arresting officer suspects drug impairment, the officer may request an evaluation by a Drug Recognition Expert, commonly called a DRE. A DRE is a law enforcement officer who has completed added training in identifying signs associated with categories of drugs.
A DRE evaluation may include:
- An interview with the arresting officer
• A preliminary examination and first pulse reading
• Eye examinations
• Divided-attention tests
• Vital-sign measurements
• Dark-room examinations
• Muscle-tone observations
• A check for possible injection sites
• Statements from the driver
• A toxicological sample
The DRE then forms an opinion about whether the person appears impaired, whether the apparent impairment may relate to drugs or a medical condition, and which drug category may be involved.
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A DRE opinion is evidence. It is not an automatic or infallible medical diagnosis.
A defense attorney may examine whether:
- The officer followed the required evaluation process
• Measurements were recorded accurately
• Medical conditions could explain the observations
• The officer considered fatigue, panic, dehydration, illness, or injury
• The predicted drug category matched the laboratory result
• Video evidence supports the written report
• Questions were leading, repetitive, or confusing
A mismatch between the claimed signs of impairment and the toxicology findings may affect the strength of the prosecution’s case.
How Blood Testing Is Used in Colorado Drug DUI Cases
In a suspected drug DUI case, police may seek a blood sample. A laboratory may test the sample for active THC, prescription medications, controlled substances, or combinations of substances.
Colorado law allows a permissible inference that a driver was under the influence of one or more drugs when the driver’s whole blood contains five nanograms or more of delta-9 THC per milliliter at the time of the offense or within a reasonable time afterward. This level does not create automatic guilt. The prosecution’s case may still depend on driving behavior, physical observations, statements, test performance, toxicology evidence, and the reliability of the testing process.
Drug concentration does not measure impairment in the same manner for every person. Active THC levels may change between the time of driving and the time of the blood draw. Prescription medication may appear in a blood sample even when the medication was taken as directed. A laboratory may also identify inactive metabolites that show prior exposure without proving impairment at the time of driving.
A defense review may address:
- Whether police had legal grounds to request or obtain the sample
• Whether the blood draw was performed correctly
• Whether the collection tubes were labeled, sealed, stored, and transported properly
• Whether the laboratory followed validated testing procedures
• Whether the result identified an active substance or only a metabolite
• Whether the reported concentration supports impairment at the time of driving
• Whether multiple substances affected the laboratory interpretation
• Whether the testing records reveal contamination, calibration, or chain-of-custody concerns
Learn more about marijuana-related defense:
https://www.hebetsmccallin.com/denver-marijuana-defense-attorneys/
Other Evidence Police May Collect
Police may try to strengthen a drug DUI case with evidence beyond roadside testing and blood results. Officers may search a vehicle when they have valid consent, a warrant, probable cause, or another recognized legal basis.
Police may document cannabis packaging, prescription bottles, drug paraphernalia, open containers, or substances found inside the vehicle. Investigators may also collect:
- Body-camera and dash-camera recordings
• Event parking-lot surveillance footage
• Witness statements
• Dispatch audio and 911 calls
• Receipts and electronic payment records
• Phone data obtained through lawful legal process
• Photographs of the vehicle and roadway
• Statements made at the police station or hospital
Possession of lawful medication or a legal cannabis product does not, by itself, prove impaired driving. The prosecution must still connect the evidence to the driver’s condition and ability to operate the vehicle safely.
How a Defense Attorney Reviews the Investigation
A defense review should examine the complete sequence of events, not only the blood result. The first issue is whether the officer had a lawful basis for the traffic stop. Other issues include probable cause for arrest, the accuracy of the officer’s observations, the quality of the recordings, and the handling of the chemical sample.
A Colorado drug DUI attorney may:
- Compare police reports with body-camera and dash-camera footage
• Review the DRE report and the officer’s training records
• Examine whether roadside instructions were clear and properly administered
• Consult a toxicology professional when the scientific evidence requires review
• Challenge an unlawful stop, arrest, search, or seizure
• Identify medical and environmental explanations for reported symptoms
• Review laboratory records and chain-of-custody documents
• Evaluate whether prosecutors can prove impairment rather than drug presence alone
Hebets & McCallin P.C. includes former prosecutors who understand how the government organizes DUI evidence and where weaknesses may appear.
Additional information is available at:
https://www.hebetsmccallin.com/denver-dui-lawyers/
https://www.hebetsmccallin.com/denver-drug-crimes-attorneys/
What to Do After a Summer Event Drug DUI Arrest
Keep all paperwork related to the arrest, including the summons, bond documents, property inventory, and any notice concerning your driving privilege.
As soon as possible, write down what you remember about:
- The route you drove
• The reason the officer gave for the stop
• The officer’s questions and instructions
• The condition of the road and shoulder
• The lighting, weather, temperature, and traffic
• The timing of any medication or cannabis use
• The roadside exercises and DRE evaluation
• The blood draw and the people involved
Preserve event tickets, parking receipts, photographs, location data, and messages that may help establish a timeline. Do not post details about the arrest on social media. Online statements may be misunderstood or used by the prosecution.
Speak with an attorney before giving additional statements to police, prosecutors, investigators, or potential witnesses.
Speak With a Colorado Drug DUI Defense Attorney
A drug DUI accusation after a summer event may involve police opinions, body-camera footage, medical information, DRE findings, and laboratory testing. Each part of the investigation should be reviewed before conclusions are drawn about impairment.
Hebets & McCallin P.C. serves clients in Denver, Colorado, and nearby areas. The firm can review the traffic stop, roadside testing, DRE evaluation, arrest, blood draw, and laboratory evidence.
Call 303-854-6006 to request a no-cost consultation about your case.
This article is for general informational purposes only and is not legal advice. Every case is different. Speak with an attorney about your specific circumstances.
