How the Breath Test Works

San Antonio Corpus Christi and Laredo DWI Defense

Intoxication was originally defined by blood alcohol testing. The amount of alcohol concentration in a person’s blood was compared to the legal definition of intoxication to determine if a person would be arrested for drunk driving. Even though this was an accurate way to test for intoxication, this procedure had many flaws:

  • It required a trained medical professional to administer the test.
  • It was an invasive procedure.
  • The analysis of the test depended upon precise procedures by trained lab technicians.
  • The results were not immediate,
  • and The test was costly.

In the 1930s, researchers discovered that a small percentage of alcohol in the blood is exhaled through the lungs. The alcohol in the breath was in direct proportion to the concentration of alcohol in the blood. Thus the breath alcohol test was born.

Over the years many different types of breath alcohol testing equipment have been invented:

  • Wet Chemistry
  • Photo Spectroscopy
  • Gas Chromatography
  • Infra Red Spectroscopy
  • Semi-Conductor Sensors (Tin Oxide Sensors)
  • Electro Chemical Analysis (Fuel Cell)

Each of the above mentioned devices require a trained operator, proper maintenance, and a properly administered test before an accurate reading can be achieved. Furthermore, some of these devices are affected by atmospheric pressure, or outside temperature. These tests can be accurate, but there are too many variables that can alter the results to consider them absolutely reliable.

That is why an experienced defense attorney is critical to your defense. A knowledgeable San Antonio driving while intoxicated lawyer will know the best way to present your defense. A DWI lawyer may be able to discredit a breath alcohol test or even have the breath test evidence thrown out entirely. If you or a loved one has been charged with DWI do not give up. Do not assume that you are defeated. Too much is at stake. Do not say anything to the police or prosecutors. Contact us for a free consultation. Let us evaluate the evidence and determine the best course of action to defend your rights, your job, and your freedom. Call us at The Law Offices of Carabin & Shaw .