Anyone facing allegations of drunk driving knows the importance of accurate numbers. Afterall, the difference between moving forward with charges or getting your case dropped can come down to the numbers the state claims represent your blood alcohol concentration (BAC). When a Colorado DUI investigation turns on a number, the two most common tools prosecutors use to build their case are those derived from either a breath test or a blood draw. Both can be accurate when properly administered, but can also produce misleading results when procedures are not followed. Understanding where errors arise can help drivers evaluate whether a reported BAC is reliable.
Breath tests: accuracy and common pitfalls
Even with regular maintenance and operator training, breath testing is an indirect measurement that estimates blood alcohol based on breath, which creates opportunities for error. Common breath test issues that affect accuracy can include:
- Calibration and maintenance: It is important that officials check and calibrate instruments on schedule. Missed inspections, failed accuracy checks or incomplete logs bring accuracy into question.
- Observation and timing: Breath testing protocols typically require an observation period to reduce the risk of mouth alcohol from recent drinking, burping or regurgitation. Testing too soon can inflate results.
- Medical and physiological factors: GERD, acid reflux, diabetes and certain diets are known to contribute to mouth alcohol or compounds that may interfere with some devices. Breathing patterns and temperature can also affect readings.
- Operator error: Improper instructions, inadequate observation or incorrect administration can introduce variability.
The takeaway is that breath results depend heavily on strict compliance with procedure and documentation.
Blood tests: accuracy and what can go wrong
Blood testing is often viewed as the gold standard because it measures alcohol directly in blood. Colorado law generally allows a driver to choose a blood test in many circumstances, and blood evidence can be powerful but it is vulnerable to collection and handling problems.
Issues can include:
- Timing and rising BAC: Alcohol absorption continues after driving. A blood draw taken later can be higher than the BAC at the time of driving, depending on drinking pattern and food intake.
- Collection and preservatives: Improper tube type, inadequate preservative or contamination can lead to fermentation or degradation that skews results.
- Chain of custody: If the sample is mislabeled, stored improperly or transferred without clear documentation, the defense may challenge whether the tested sample is truly the driver’s.
- Laboratory procedures: Instrument calibration, analyst training and quality control all matter. Errors in testing or reporting can occur.
These issues can invalidate the results.
It is important to review these records when facing drunk charges to check for any of the potential issues noted above. This can serve as an important tool in one’s defense strategy.
Breathalyzers and blood tests can both produce reliable BAC evidence, but neither is immune from human error, timing issues or documentation gaps. In Colorado DUI cases, the most important question is often not the number itself but whether the testing process and records support trusting that number.