DWI/DUI Practice Center

Challenging the Breathalyzer Test

Fighting Unreliable Breathalyzer Test Results Under Texas State Law

The blood-alcohol concentration (BAC) limit for drivers 21 and over in Texas is 0.08. In order to convict you of a drunk-driving charge, the State of Texas must show that you were driving while your BAC was over that legal limit. To prove it, authorities must take a sample of your blood, breath or urine. Most police agencies rely on a breath test to make their cases, or use it first when making an arrest. But as evidence mounts that breathe tests have serious flaws, more and more drivers are able to avoid a DWI conviction by challenging the reliability of their test results in court. Carabin Shaw attorneys can tell you whether the facts of your case make it a good candidate for this kind of defense.

There Are Many Ways to Dispute Breath Test Results

Breath tests work by measuring the amount of alcohol in one exhale. Scientists believe the result from that measurement corresponds directly to how much alcohol is in your blood; breath tests use a formula to calculate a BAC from an exhale. But because this is an indirect method of measuring blood-alcohol concentration, there are many variables that can "throw off" the test, causing it to give false negatives or false positives. And of course, that means the test results can be questioned. Breath tests can be thrown off by:

  • air temperatures the device wasn't calibrated for
  • variations in barometric pressure
  • genetic variations in blood chemistry
  • differences in individuals' physical fitness or activity levels
  • how fast the individual being tested is breathing
  • how well the person conducting the test understands it
  • the age and quality of the testing equipment
  • whether the individual being tested was exposed to certain fumes or chemicals
Judges in many places have permitted DWI/DUI lawyers to bring experts to testify on these and other flaws in the tests that could give their clients a false positive. But not all judges are willing to hear these types of challenges.

Most drivers know that they weren't necessarily drunk just because they "blew" a certain BAC reading. The same goes for your court case -- you don't necessarily have to plead guilty just because you tested at 0.08 or higher. Even if you were above the limit, Carabin Shaw attorneys can help you find the most relevant flaws in your individual test and use them to weaken the prosecution's case against you, or even have the test thrown out. Located in San Antonio, we represent clients charged with DWI and other drunk driving violations in Bexar County and the surrounding areas.

Our office also offers a bail bond service and can advise you through the bail proceedings.

Contact Carabin Shaw today for experienced representation in driving while intoxicated (DWI) legal matters. Your first consultation is free, so send us an email or call 210.222.2288.