Challenging BAC Results in Nevada DUI Cases
The State's BAC number is a starting point, not a conclusion. Breath and blood testing is subject to error at every stage — from collection and calibration to storage and analysis. Whether that number holds up depends on how it was obtained.
In many DUI cases, the State relies heavily on a blood alcohol concentration result to prove guilt. Prosecutors often treat these numbers as definitive. They are not.
BAC results can be inaccurate, improperly obtained, or misinterpreted. Chemical testing — whether breath or blood — is subject to error. Machines malfunction, procedures are not always followed, and human error can affect the outcome at every stage. A reported BAC number is only as reliable as the process used to generate it.
A strong DUI defense begins with a careful examination of how that number was produced — and whether it can withstand scrutiny.
Challenging breath test results
Challenging blood test results
Timing, absorption, and the two-hour rule
BAC results are often taken well after the time of driving. Alcohol absorption is not instantaneous — if a person was still absorbing alcohol when the test was administered, the result may overstate the BAC at the moment the vehicle was in motion. This is sometimes called the rising BAC defense, and it is a recognized challenge in cases where the gap between driving and testing is meaningful.
Nevada's two-hour rule requires that testing occur within two hours of driving to support a per se charge. But even a test taken within that window does not automatically establish the BAC at the time of driving. The timing of absorption, the defendant's drinking pattern, and the interval between the last drink and the test all bear on what the result actually means.
Individual variability and BAC accuracy
BAC does not affect everyone the same way, and a single number does not tell a complete story. Body composition, food intake, metabolic rate, and drinking pattern all influence how alcohol is absorbed and eliminated. The standard elimination rate used in forensic calculations — roughly 0.015% per hour — is a population average, not a biological constant. Applying it to a specific individual introduces error.
These variables are relevant both to the accuracy of the reported result and to what that result actually reflects about the defendant's condition at the time of driving. They are legitimate subjects for defense expert testimony and can introduce meaningful doubt about the prosecution's interpretation of the number.
A BAC result will likely be central to the State's case. That does not mean it is accurate or unchallengeable.
Free Consultation →How we challenge BAC evidence
Maintenance and calibration records
Every breath device used in the arrest is examined for calibration history, service records, and any documented out-of-tolerance readings.
Police reports and procedure
The arresting officer's compliance with observation period requirements, testing protocol, and documentation standards is reviewed in detail.
Laboratory documentation
Blood test cases require full laboratory documentation — analyst notes, instrument logs, quality control records, and chain of custody forms.
Independent expert review
Where warranted, an independent toxicologist reviews the State's evidence and methodology to identify errors, inconsistencies, or alternative interpretations.
Timing and absorption analysis
The relationship between the time of driving and the time of testing is examined to assess whether the reported BAC accurately reflects the defendant's condition while driving.
Per se vs. impairment
A BAC challenge attacks the per se theory — the number itself. But the State may also pursue an impairment theory based on officer observations and field sobriety tests, independent of the test result. A complete defense addresses both. See our overview of per se vs. impairment charges.
Challenging BAC in Nevada DUI cases — frequently asked questions
Frequently Asked Questions
Clear answers to common record sealing questions.