If you are pulled over by law enforcement in Colorado and an officer suspects you have been drinking, chances are you will be asked to submit to a blood alcohol concentration (BAC) test. There are three primary methods used to measure your BAC, and each one comes with its own strengths and weaknesses. Understanding how these tests work and where they fall short can make a significant difference in how you approach a DUI charge in Denver.
At Shazam Kianpour & Associates, P.C., we know that the results of a BAC test can determine the direction of your entire case. With more than 22 years of experience defending clients throughout Colorado against DUI and traffic charges, our team understands how to identify testing errors that could work in your favor. Whether you submitted to a breath, blood, or urine test, a closer look at the circumstances surrounding your results may reveal weaknesses the prosecution does not want you to find.
How Breath Tests Work in Colorado
Breath tests, commonly administered through a Breathalyzer device, are the most frequently used method for estimating BAC during a traffic stop. The device works by measuring the amount of alcohol that passes through the lungs and is expelled into your breath. While breath tests provide rapid results and are convenient for officers in the field, they are considered less accurate than blood tests in Colorado.
Colorado imposes strict procedural requirements before a breath test can be considered valid. No tobacco or other substances can be present in your mouth, and a minimum of 20 minutes must have passed since you last burped or belched. You also need to produce enough air for the machine to register a reading. If any of these requirements are not met, the test results may not be admissible in court, which is why working with a knowledgeable criminal defense attorney who understands these technicalities is essential.
Timing Can Work Against You With a Breath Test
One important factor to consider is timing. Police can generally transport you to a station relatively quickly after a stop. Because alcohol absorption continues for a period after your last drink, taking a Breathalyzer test soon after being pulled over may produce a higher reading than a test administered later. This means your result could reflect a BAC that does not accurately represent your level of impairment at the time you were actually behind the wheel.
What to Know About Blood Tests
A blood test is generally considered the most accurate method for determining BAC. According to MedlinePlus, a service of the National Library of Medicine, a BAC blood test measures the amount of alcohol present in a blood sample and can detect alcohol for up to 12 hours after consumption (MedlinePlus, 2025). Because a blood draw usually requires a trip to a hospital or medical facility, there is often a delay between the traffic stop and the actual test. This extra time gives your body the opportunity to metabolize more alcohol, which could result in a lower BAC reading compared to a breath test taken immediately.
However, blood tests are not without their flaws. Consent is typically required before a blood draw, and refusing the test can carry its own legal consequences. Lab errors such as improper sterilization, lack of preservatives or refrigeration, vial mix-ups, coagulation, and even fermentation of blood in the vial can all compromise the accuracy of results.
Other Substances Can Complicate Blood Test Results
Another consideration with blood tests is that they can detect substances beyond alcohol. If marijuana or other drugs are present in your system at the time of the draw, those substances will appear in your results as well. This means that even if your BAC falls below the legal limit, you could still face additional charges related to driving under the influence of drugs.
Urine Tests Are the Least Reliable Option
Urine tests are the least common and least accurate method for measuring BAC. They are typically only administered when breath and blood tests are not available. Urine test results tend to be significantly higher or lower than a person’s actual BAC because urine reflects alcohol processed over time rather than what is currently in the bloodstream. Alcohol can take up to two hours to appear in urine and may remain detectable for up to 24 hours, making it difficult to prove impairment at the specific time of a traffic stop.
Because of these limitations, urine test results are often the most vulnerable to challenge in court. An experienced defense attorney can scrutinize the circumstances under which a urine test was administered and highlight the inherent unreliability of this method to cast doubt on the prosecution’s case.
Protect Your Rights With a Fearless Defense Team
Every BAC test, regardless of the method used, can be challenged when proper procedures are not followed or when scientific limitations undermine the reliability of the results. At Shazam Kianpour & Associates, P.C., our attorneys have the trial skills and negotiating experience to examine every detail of your case and fight for the outcome you deserve. As a National Trial Lawyers and Super Lawyers award recipient, Mr. Kianpour and our team are committed to providing the personal attention that larger firms cannot match.
If you are facing a DUI charge in Colorado, do not assume that a BAC test result seals your fate. Contact us today for a consultation and put a fearless fighter in your corner.
References:
Blood Alcohol Level. MedlinePlus. Updated 2025. Available at: https://medlineplus.gov/lab-tests/blood-alcohol-level/