Challenging Breathalyzer Results in DUI Cases

A DUI charge can have serious legal and personal consequences, but breathalyzer results are not always as reliable as prosecutors claim. These tests, often the primary evidence in DUI cases, are subject to errors, misinterpretation, and external influences that can lead to inaccurate BAC readings. 

Understanding the flaws in breathalyzer testing—and how a strong legal defense can challenge their validity—may be the key to protecting your rights. If you are facing DUI charges in Orange County, it is important to know your options and seek skilled legal representation.

How Breathalyzer Tests Work

When you consume alcohol, traces of it enter your bloodstream, and your blood alcohol content (BAC) measures the percentage of alcohol present. To determine BAC, law enforcement officers often use a breathalyzer, a device that estimates alcohol levels by analyzing a person’s breath. 

In California, it is illegal to drive if your BAC exceeds the following limits:

• 0.08% or higher if you are 21 years or older
• 0.01% or higher if you are under 21 years old
• 0.01% or higher at any age if you are on DUI probation
• 0.04% or higher if you are operating a commercial vehicle
• 0.04% or higher if you are driving a passenger for hire

Factors That Can Lead to Inaccurate Readings

A study published in the National Library of Medicine found that breathalyzer readings can deviate by up to 50% from actual blood alcohol levels. This discrepancy means that a breathalyzer test may not always provide an accurate measure of intoxication, potentially resulting in unjust DUI charges.

Numerous external and physiological factors can impact breathalyzer accuracy. Below are some of the most common issues that can cause false or inflated BAC readings:

Mouth Alcohol Contamination

Residual alcohol from mouthwash, breath sprays, or acid reflux can cause artificially high BAC readings. If alcohol remains in the mouth, rather than being absorbed into the bloodstream, a breathalyzer may detect an elevated BAC that does not accurately reflect intoxication levels.

Improper Calibration

Breathalyzers must be regularly maintained and calibrated to ensure accuracy. If a device is not serviced at proper intervals, it may yield unreliable BAC readings, which could unfairly impact a DUI case.

Environmental Interference

Temperature changes, humidity, and exposure to chemicals (such as paint fumes or gasoline) can interfere with breathalyzer sensors, leading to false-positive readings. External factors may cause the device to misinterpret substances in the breath as alcohol.

Medical Conditions

Individuals with diabetes, acid reflux (GERD), or those following high-protein diets may experience acetone breath, a condition where the body produces elevated acetone levels as a byproduct of metabolism. Since some breathalyzers cannot distinguish between acetone and ethanol, they may register falsely high BAC readings, even in the absence of alcohol consumption. 

Challenging Breathalyzer Test Results

Breathalyzer results are often a key piece of evidence in DUI cases, but their accuracy depends on both proper administration and the reliability of the device itself. A DUI defense attorney can examine multiple factors to challenge the accuracy and admissibility of breathalyzer evidence.

Breathalyzer tests can be challenged on two main grounds: errors in how the test was administered and flaws in the accuracy of the device itself. Below, we break down these key areas of concern.

Errors in Breathalyzer Administration

Breathalyzer tests must be conducted according to strict legal procedures. If law enforcement fails to follow proper protocols, the results may be unreliable and inadmissible in court. Key factors that can invalidate a breathalyzer test include:

• Failure to Follow Testing Protocols – Officers must adhere to standardized procedures when conducting breath tests.
• Ignoring the 15-Minute Observation Period – In California, officers must observe the suspect for at least 15 minutes before administering the test to ensure no contamination from burping, regurgitation, or residual mouth alcohol.
• Lack of Proper Training – If the officer administering the test was not properly trained or certified, the results can be challenged in court.

Flaws in Breathalyzer Reliability

Beyond procedural errors, the accuracy of the breathalyzer device itself can be questioned. A defense attorney may investigate:

• Breathalyzer Maintenance and Calibration Records – Devices must be regularly serviced to ensure accuracy. A history of missed calibrations or malfunctions can undermine BAC readings.
• Device Malfunctions and Software Errors – Defective sensors, incorrect software updates, or outdated technology can cause false positives.
• Professional Testimony on Breathalyzer Limitations – A forensic specialist can explain to the court how environmental factors, medical conditions, or testing errors may have led to inaccurate BAC readings.

Protect Your Rights with an Experienced Orange County DUI Defense Attorney

Breathalyzer results are not always definitive, and challenging them could be the key to avoiding a conviction. At the Law Offices of William Bruzzo, we have 30 years of experience defending DUI cases and navigating the Orange County court system.

Call our law firm today at (714) 547-4636 or contact us online to discuss your DUI case and explore your defense options.