How Breathalyzers Work in Texas DWI Arrests
San Antonio police officers rely heavily on breathalyzers to determine blood alcohol concentration (BAC) during DWI arrests. These devices measure alcohol vapor in a person’s breath and convert that reading into a BAC percentage. Under Texas law, a BAC of 0.08% or higher means a driver is legally intoxicated. However, breathalyzer technology often delivers flawed results. Small errors in administration, medical conditions, or even extreme San Antonio weather can lead to readings that are not scientifically reliable. Knowing how these devices function allows a DWI lawyer to find weaknesses in the state’s case.
SAPD and Bexar County Breathalyzer Devices: Maintenance and Calibration Issues
The San Antonio Police Department (SAPD) and Bexar County Sheriff’s Office use approved machines like the Intoxilyzer 9000. These devices must undergo strict maintenance, calibration, and inspection to remain accurate. When officers skip calibration checks or agencies fail to maintain logs, the machine’s results become questionable. Defense attorneys often request machine maintenance records to expose gaps in compliance. In some cases, Bexar County judges have ruled breathalyzer results inadmissible because agencies ignored required testing protocols. A strong San Antonio DWI defense lawyer knows how to uncover and exploit these weaknesses.
How Temperature Affects Breath Test Results
Breathalyzers assume a normal body temperature of 98.6°F. A driver with a fever, heat exhaustion, or exposure to San Antonio’s extreme summer heat can produce artificially high BAC readings. Similarly, the machines themselves function best within controlled temperature ranges. If officers administer tests in scorching weather or fail to store devices properly, the sensors may misread results.
Chart: Factors That Skew Breathalyzer Accuracy
| Factor | Effect on Results |
| High body temperature | Increases BAC reading |
| Diabetes (acetone) | Mimics alcohol presence |
| GERD or acid reflux | Causes mouth alcohol contamination |
| Machine miscalibration | Inflates or lowers BAC |
| Officer error | Improper test administration |
Medical Conditions That Mimic High Blood Alcohol Levels
Medical conditions often trigger false positives on breath tests:
- Diabetes: Diabetic ketoacidosis causes high acetone levels in breath. Breathalyzers may interpret acetone as alcohol, inflating BAC readings.
- GERD (Acid Reflux): When stomach acid or alcohol vapors rise into the throat, breath samples show artificially high results.
- Asthma Inhalers: Certain chemical compounds in inhalers skew readings upward.
Someone suffering from these conditions may blow a result over 0.08% even when sober. An experienced San Antonio DWI defense attorney introduces medical records and expert testimony to challenge these flawed tests.
Common Defense Strategies to Challenge Breathalyzer Results in San Antonio
A skilled San Antonio DWI lawyer uses several strategies to question breathalyzer accuracy:
- Maintenance Records: Demanding SAPD and Bexar County machine logs to reveal improper calibration.
- Officer Training: Exposing failures in officer certification or test procedure.
- Medical Evidence: Presenting proof of health conditions that mimic intoxication.
- Environmental Factors: Showing how Texas heat, cold, or poor storage compromised accuracy.
By raising doubt about scientific reliability, a defense attorney makes it harder for prosecutors to rely on breathalyzer results.
What to Do if Your Breathalyzer Result Feels Wrong
Many people in San Antonio assume a breathalyzer reading seals their fate in a DWI case. That belief is false. Courts in Bexar County know these machines are not perfect. Judges and juries often side with defendants when lawyers present clear evidence of errors, medical complications, or poor police practices. If your breathalyzer result feels wrong, do not accept it at face value. Contact a criminal defense lawyer immediately to protect your rights.
Call a San Antonio DWI Lawyer Today
A questionable breathalyzer result should never destroy your future. At Ried Pecina Trial Lawyers, we fight aggressively to challenge unreliable evidence and defend your freedom. We understand the science, the law, and the tactics prosecutors use in San Antonio and Bexar County courts. Call (210) 893-0000 today for a free consultation with a trusted San Antonio DWI lawyer who will protect your license, your career, and your future.
