Key Strategies for Challenging Breath Test Results
Driving while intoxicated (DWI) charges often rely on blood and breath test results as primary evidence. However, these tests aren’t always accurate, and challenging the results can be a crucial part of a strong DWI defense.
At The Law Office of Justin K. Hall P.C., I have spent decades defending individuals accused of DWI in Rockwall, Texas, and surrounding areas. Breath test machines aren’t infallible, and knowing how to dispute their reliability can make a significant difference in a case.
A strong defense requires understanding the science behind breath tests, potential errors in their administration, and the legal options available to challenge the results.
A breathalyzer result alone doesn’t automatically mean a conviction. Several factors can affect the accuracy of a breath test, from improper administration to medical conditions that produce false readings.
Many people are unaware that law enforcement officers are required to follow specific procedures when conducting breath tests, and any deviation from these protocols can call the results into question.
For those facing DWI charges, understanding how to challenge breath test results is essential to building a strong defense. By exploring the science behind breath testing, potential errors, and legal strategies, I can create a well-rounded approach to defending against these charges.
The Science Behind Breath Tests and Their Weaknesses
Breath tests measure blood alcohol concentration (BAC) by analyzing the alcohol content in a person’s breath. The assumption is that the alcohol level in the lungs reflects the alcohol in the bloodstream, but several factors can interfere with this measurement.
Common issues with breath tests include:
Mouth alcohol contamination: Residual alcohol in the mouth from mouthwash, medication, or recent drinking can inflate BAC readings.
Improper machine calibration: Breathalyzers must be regularly calibrated to remain accurate.
Medical conditions: Acid reflux, diabetes, and certain diets can create false positives.
Environmental factors: Fumes from paint, gasoline, or chemicals can affect test results.
Even though breathalyzers are widely used, their scientific reliability remains questionable. The human body doesn’t metabolize alcohol in a uniform way, meaning that BAC levels can fluctuate based on weight, metabolism, hydration levels, and even recent meals.
Additionally, not all individuals exhale alcohol in the same way, making breath tests an imperfect measurement of actual intoxication levels. Because of these potential issues, courts have recognized that breathalyzer results alone aren’t always enough to secure a conviction.
This is why a DWI defense strategy should include questioning the reliability of the breath test and exploring alternative explanations for the BAC reading.
Questioning the Accuracy of the Breathalyzer Device
Breathalyzers require careful maintenance and calibration to provide accurate results. If the device used in an arrest wasn’t properly maintained, its readings could be flawed.
Potential issues with breathalyzer devices include:
Improper calibration: Law enforcement agencies must regularly calibrate and test breathalyzers.
Software malfunctions: Some devices have reported software errors that affect accuracy.
Operator error: Officers must be properly trained to administer tests correctly.
Lack of certification: If the device wasn’t approved for use in Texas, its results may not be admissible.
Breathalyzer machines function based on fuel cell and infrared spectroscopy technology, but these methods aren’t foolproof. Calibration issues can cause readings to fluctuate, and some devices are known to have high margins of error.
Additionally, different models of breathalyzers have different levels of sensitivity, meaning the same person could blow different BAC results on different machines. When questioning a breathalyzer's accuracy, examining its calibration records and maintenance logs can expose errors that could lead to the suppression of the results in court.
An effective DWI defense involves scrutinizing these records to identify inconsistencies or negligence in the maintenance of the device.
Examining the Arrest Process for Errors
Law enforcement must follow strict procedures when conducting a DWI investigation. Any procedural mistakes can cast doubt on the validity of the breath test results.
Common procedural errors include:
Failure to observe the 15-minute rule: Officers are required to observe a suspect for 15 minutes before administering a breath test to rule out contamination.
Improper test administration: If an officer doesn’t follow the correct steps, the test may be invalid.
Lack of probable cause: If there was no valid reason for the traffic stop, any evidence collected—including breath test results—could be suppressed.
Failure to inform the suspect of their rights: If officers didn’t properly advise the suspect of their rights, this could weaken the prosecution’s case.
When law enforcement fails to follow established procedures, the validity of their evidence becomes questionable. The 15-minute observation rule is particularly important because failure to adhere to it can result in falsely elevated BAC levels.
Reviewing arrest records, dash cam footage, and body cam footage can reveal inconsistencies that may help challenge the breath test results. Even small procedural errors can be enough to create doubt about the accuracy of the breathalyzer reading and the fairness of the arrest process.
This is where a strong DWI defense can highlight law enforcement mistakes that may lead to evidence being thrown out.
Challenging the Officer’s Interpretation of Signs of Intoxication
Many DWI cases include an officer’s observations, such as slurred speech, bloodshot eyes, or the smell of alcohol. However, these signs are subjective and can have alternative explanations.
Alternative causes for common signs of intoxication include:
Fatigue: Lack of sleep can cause bloodshot eyes and slow reaction times.
Allergies or illness: Congestion or medication can lead to slurred speech.
Nervousness: Anxiety during a traffic stop can result in unsteady behavior.
Environmental factors: Strong odors from food or medication can be mistaken for alcohol.
An officer’s observations aren’t always reliable indicators of intoxication. Many people exhibit nervous behavior when stopped by law enforcement, which can be mistaken for impairment.
Some medical conditions, such as hypoglycemia, can also mimic signs of intoxication, further complicating the officer’s ability to make an accurate judgment. In cross-examinations, pointing out inconsistencies in the officer’s testimony or offering alternative explanations for their observations can help undermine the prosecution’s case.
Utilizing Witness Testimony
Witnesses can provide testimony on the inaccuracies of breath tests and procedural flaws. Their analysis can reinforce arguments that the breath test results are unreliable. Many breathalyzer devices rely on outdated technology, and professional testimony can demonstrate the flaws in these machines, showing how even minor errors can produce unreliable readings.
Professionals can also evaluate the specific circumstances of the test, including how long the suspect waited before blowing into the device and whether external factors might have influenced the result. Their findings can be crucial in establishing reasonable doubt in a DWI case.
Incorporating professional witness testimony into a DWI defense can significantly strengthen arguments against the prosecution’s evidence.
Types of professionals who can assist include:
Toxicologists: They can explain how breath test machines work and why results may be inaccurate. Additionally, they can analyze BAC fluctuations and how external variables—such as medication or diet—can impact test results.
Medical professionals: They can testify about medical conditions that affect BAC readings, such as GERD, diabetes, or metabolic disorders, which may create misleading alcohol readings.
Breathalyzer consultants: They can analyze maintenance records and demonstrate device malfunctions. If the breathalyzer used was improperly calibrated or not maintained according to regulatory guidelines, their findings can significantly weaken the prosecution’s case.
Presenting professional testimony can help cast doubt on breath test reliability, providing a strong defense strategy.
Exploring Alternative Explanations for High BAC Readings
Sometimes, a person’s BAC reading may be artificially high due to factors unrelated to alcohol consumption. Certain health conditions and dietary choices can result in breath test readings that don’t accurately reflect a person’s intoxication level.
The body’s metabolic processes can produce compounds that mimic alcohol, leading to inflated BAC readings. Additionally, the way a breathalyzer detects alcohol isn’t always reliable because it assumes a standard breath-to-blood alcohol ratio, which can vary significantly between individuals.
Factors that can cause inflated BAC readings include:
Residual mouth alcohol: Alcohol in the mouth from recent drinks, mouthwash, or medicine can produce false readings. Even certain dental procedures or breath sprays can leave residual alcohol that may lead to incorrect test results.
Auto-brewery syndrome: A rare condition where the body produces alcohol due to gut fermentation. In some cases, individuals with this syndrome may register high BAC levels without consuming any alcoholic beverages.
Ketosis from low-carb diets: Certain diets produce acetone, which can be misread as alcohol. When the body enters ketosis, it releases acetone through the breath, which some breathalyzers detect as ethanol.
Medical conditions: GERD, diabetes, and asthma inhalers can impact test results. Acid reflux, for example, can cause stomach alcohol to rise into the esophagus, leading to artificially high BAC readings.
If any of these factors apply, they can be used to challenge the prosecution’s reliance on breath test results. A well-prepared DWI defense will take these alternative explanations into account to cast doubt on the accuracy of the BAC reading.
Contact an Experienced DWI Lawyer
Challenging breath test results requires an aggressive defense and a deep understanding of the law. At The Law Office of Justin K. Hall P.C., I have defended countless individuals in Rockwall, Dallas, Collin, Hunt, and Kaufman, Texas. If you’re facing DWI charges, contact my firm today to discuss your case and explore your legal options.