Breathalyzer Evidence in Court: How Defense Attorneys Challenge Test Results

Breathalyzer tests are often central pieces of evidence in DUI cases, widely viewed by law enforcement as reliable indicators of a driver’s blood alcohol content (BAC). However, these tests are not infallible. Houston DWI Defense attorneys frequently challenge breathalyzer evidence in court, leveraging scientific, procedural, and legal arguments to undermine the credibility of test results.

Understanding how breathalyzer evidence can be contested is crucial for those facing DUI charges, as a robust defense strategy can sometimes lead to reduced penalties or case dismissals.

1. Questioning Breathalyzer Accuracy and Reliability

Breathalyzer devices work by measuring the amount of alcohol in a person’s breath and converting it into an estimated blood alcohol concentration. However, breathalyzers have known limitations that can lead to inaccurate results. A skilled defense attorney may point out factors that can compromise the reliability of these devices, including:

Calibration Issues: Breathalyzer devices require regular calibration to ensure accuracy. If a device isn’t correctly calibrated, it can give an inaccurate reading. Defense attorneys often request maintenance and calibration records to examine if the device was properly maintained.
Sensitivity to Temperature Changes: Breathalyzers can be sensitive to ambient temperature changes, which may affect readings. For instance, if the device was left in a police car under extreme conditions, it might not function correctly. Demonstrating this can cast doubt on the reliability of the reading.
Substance Interference: Breathalyzers are designed to detect ethanol (the type of alcohol found in beverages), but they can sometimes react to other chemicals, giving false readings. Certain medications, mouthwash, and even some diets can cause elevated readings. Defense attorneys may introduce evidence showing that other substances could have skewed the results.

2. Challenging Breathalyzer Test Administration Procedures

Improper administration of breathalyzer tests can lead to erroneous results. Defense attorneys frequently investigate the training and actions of the officer who conducted the test to identify procedural errors, including:

Operator Certification and Training: Law enforcement officers must undergo specific training to administer breathalyzer tests. If the officer who conducted the test was not certified or properly trained, the attorney may argue that the test results are unreliable and should be excluded.
Observational Period Requirement: Most states require that the officer observe the suspect for a set period (usually 15-20 minutes) before administering the test. This observation period is meant to ensure that the individual hasn’t consumed food, drink, or substances that could influence the reading. Failure to adhere to this requirement can be grounds for dismissal of the test results.
Improper Use of Device: Breathalyzer devices require specific handling for accurate results. If the officer mishandled the device, failed to follow standard procedures, or performed the test incorrectly, a defense attorney could argue that the results are invalid.

3. Presenting Alternative Explanations for BAC Levels

There are cases where breathalyzer results reflect a high BAC level even if the driver wasn’t impaired. Defense attorneys may argue that the driver’s BAC level was elevated due to reasons unrelated to recent drinking. Some defenses include:

Residual Mouth Alcohol: When a person drinks, small amounts of alcohol can linger in the mouth, especially if the driver burped, vomited, or had dental work that could trap alcohol. Residual alcohol in the mouth can lead to an inaccurately high BAC reading, as the breathalyzer measures this “leftover” alcohol instead of the alcohol from deep lung air.
Medical Conditions: Certain medical conditions, like gastroesophageal reflux disease (GERD), acid reflux, and diabetes, can lead to higher BAC readings. GERD and acid reflux can bring stomach contents, including alcohol, into the mouth, causing artificially high readings. Diabetics with high blood sugar can produce acetone, which breathalyzers may interpret as ethanol.
Ketosis from Low-Carb Diets: Ketogenic diets and fasting can lead to a state called ketosis, where the body produces ketones for energy. These ketones can create isopropyl alcohol in the body, which some breathalyzers may detect as ethanol, resulting in an inaccurately high BAC reading.

4. Leveraging Expert Witness Testimony

Expert witnesses play a crucial role in challenging breathalyzer evidence. Defense attorneys often hire forensic toxicologists or other experts to scrutinize the breathalyzer test results and provide an alternative perspective. An expert can:

Explain the Limitations of Breathalyzers: A toxicologist or chemist can testify about the scientific limitations of breathalyzer technology, shedding light on potential inaccuracies that may not be immediately apparent to a jury.
Identify Testing Flaws and Device Errors: Experts can examine calibration records, device specifications, and procedural details, helping the court understand how a poorly maintained or mishandled breathalyzer might yield incorrect results.
Support Alternative Explanations for BAC Levels: In cases involving residual mouth alcohol, ketosis, or medical conditions, an expert witness can explain how these factors may have affected the breathalyzer reading.

5. Highlighting Constitutional and Legal Violations

Defense attorneys also explore possible constitutional violations that may have occurred during the traffic stop and subsequent breathalyzer test. This approach can sometimes lead to the suppression of evidence if the court finds the violation significant enough. Common arguments include:

Unlawful Stop or Lack of Probable Cause: If the police did not have a valid reason for stopping the driver in the first place, any evidence collected, including breathalyzer results, could be deemed inadmissible in court. Attorneys may investigate the officer’s reason for initiating the stop and argue that there was no probable cause for the test.
Improper Warrantless Search: In some states, a breathalyzer test is considered a search, and constitutional protections apply. If the officer didn’t have a warrant or the driver didn’t consent to the test, the attorney may argue that the evidence was obtained unlawfully and should be excluded.

6. Statutory Time Limits on Testing

Most states require that breathalyzer tests be administered within a specific timeframe after the initial stop. If there’s a substantial delay between the stop and the test, the results may not accurately reflect the driver’s BAC at the time they were operating the vehicle. Attorneys can use this timing issue to challenge the relevance of the test results to the case.

Conclusion

Breathalyzer evidence is often perceived as definitive proof of a driver’s intoxication, but defense attorneys can challenge it on various grounds. From questioning the device’s accuracy to pointing out procedural errors, alternative explanations for BAC levels, and constitutional violations, attorneys have multiple avenues for attacking breathalyzer evidence in court.

Understanding these potential weaknesses is essential for individuals facing DUI charges, as an effective defense strategy can significantly impact the case outcome. Each case is unique, and a skilled attorney can analyze the specifics to develop a tailored approach, ultimately strengthening the defense and increasing the chances of a favorable resolution.