By: Patrick Silva, Attorneys at Law April 5, 2026

How Do Breathalyzers Actually Work and Can San Bernardino Police Records Prove They Failed?

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Driving through Redlands after an evening out should not end with handcuffs and a looming court date at the San Bernardino Justice Center. For many drivers stopped on the I-10 or near University Street, the first sign of trouble is the roadside breath test. Most people assume these handheld devices provide an infallible measurement of blood alcohol content (BAC). Law enforcement officers often treat these readings as the absolute truth, but the science behind the machines tells a different story.

Breathalyzers do not actually measure your blood alcohol content. Instead, they measure the alcohol vapor in your breath and use a mathematical formula to guess the concentration in your blood. This distinction matters because the accuracy of that guess depends on the machine working perfectly, being properly calibrated, and the driver having “normal” physiology. When any of these factors shift, the results lose their integrity.

The Science of Fuel Cell Sensors

Modern portable breath-testing (PBT) devices used by San Bernardino County Sheriff’s deputies and local police typically rely on fuel-cell technology. A fuel cell sensor consists of two platinum electrodes with an acid-electrolyte material sandwiched between them. When you blow into the device, any ethyl alcohol in your breath oxidizes as it passes over the electrodes.

This chemical reaction creates an electrical current. The device measures the current’s strength to determine the alcohol concentration. A stronger current results in a higher BAC reading on the screen. While this sounds like precise chemistry, fuel cells are not always specific to alcohol found in beverages. They can react to other chemical compounds, leading to “false positives” and unwarranted arrests in Redlands and nearby Inland Empire communities.

Why Your Body Can Trick the Machine

The primary flaw in breath testing is the assumption that every person has the same “partition ratio.” California law, specifically Title 17 of the California Code of Regulations, assumes a 2100-to-1 ratio between alcohol in the breath and alcohol in the blood (17 CCR § 1220.4). Not every human body follows this mathematical average.

Factors like body temperature, hematocrit levels, and even your breathing pattern can skew the results. If you have a fever or have just finished exercising near the Redlands Bowl, your body temperature might be higher than the machine expects. For every degree Celsius above “normal” breath temperature, a breathalyzer can overestimate BAC by approximately 7 percent.

The Hidden Impact of GERD and Digestive Issues

One common reason for a failing breathalyzer is Gastroesophageal Reflux Disease (GERD). When a person suffers from acid reflux or heartburn, stomach acid and undigested alcohol vapors can travel back up the esophagus and into the mouth. Breathalyzers are designed to measure “deep lung air,” but GERD introduces “mouth alcohol” into the sample.

Since the machine assumes the alcohol it detects is coming from deep in your lungs, the presence of refluxed alcohol can cause the BAC reading to skyrocket far beyond the legal limit of 0.08 percent, which is not a reflection of your actual impairment; it is a mechanical error caused by a medical condition. In San Bernardino County courts, showing a history of digestive issues can be a powerful tool to challenge the reliability of the prosecution’s evidence.

Understanding the Mouth Alcohol Problem

Mouth alcohol does not just come from medical conditions. It can also stem from recent consumption, dental work, or even certain mouthwashes. California Title 17 regulations require officers to conduct a continuous 15-minute observation period before administering a breath test (17 CCR § 1219.3).

During these 15 minutes, the officer must ensure you do not smoke, vomit, or put anything in your mouth. If the officer in Redlands was busy filling out paperwork or talking to a partner instead of watching you every second, they cannot guarantee the sample was free of mouth alcohol. Any burp or hiccup during that window can contaminate the results, making the breathalyzer’s final number legally unreliable.

Common Failures Found in Calibration Logs

When we analyze the maintenance history of the specific unit used in your case, we often find red flags. These include:

Inconsistent baseline readings during “blank tests.”
Failure to use a verified dry gas or liquid simulator solution during calibration.
Repair records show the sensor was replaced shortly after your arrest.
The use of expired simulator solutions that produce inaccurate “standard” benchmarks.

If the San Bernardino Sheriff’s Department cannot prove the machine was in proper working order at the time of your stop, the science they are using against you begins to crumble. A BAC reading of 0.09 percent might look like an open-and-shut case, but a faulty log can turn that number into meaningless data.

Patrick Silva, Attorneys at Law: Fighting for Your Future

The team at Patrick Silva, Attorneys at Law, understands that a DUI charge in San Bernardino County can feel overwhelming. We have spent years studying the intricacies of breathalyzer science and Title 17 regulations to provide a defense that goes deeper than the surface. We do not just accept the police report at face value; we dig into the maintenance logs, the officer’s training records, and the physiological factors that may have tainted your results. If you are facing charges in Redlands or the surrounding areas, put our experience to work for you.