Under Texas law, the legal blood alcohol concentration limit is 0.08. If you operate a motor vehicle while your BAC level is at 0.08 or higher, you could be arrested and charged with a very serious DWI offense. Some people incorrectly assume that this means that DWI cases are relatively straightforward, and if responding police officers measure a person’s BAC at 0.08 or higher, then they will be convicted. However, this is not always an easy thing to prove.

You need to be skeptical of BAC test results. For many different reasons, BAC measurements can be unreliable. One major issue that most people are completely unaware of is radio frequency interference (RFI). Devices that emit radio frequencies, including your cell phone, have the potential to mess up the results of a breathalyzer test. This means that the BAC test may incorrectly show a driver to be over the legal limit when they are actually under it – and, most importantly, this information can be used for beating a DWI charge in Texas.

What is Radio Frequency Interference (RFI)?

To understand the concept of radio frequency interference, it is first necessary to understand how breathalyzer tests actually work. Contrary to popular belief, a breath test does not actually directly measure the amount of alcohol in a person’s blood. Instead, most modern breath tests measure the amount of infrared light in a person’s mouth in order to detect the presence and concentration of ethyl alcohol. This distinction matters because radio frequency interference can affect this type of measuring system. In fact, breathalyzer test manufacturers first started to notify authorities about this issue as early as the 1980s.

Smith & Wesson, a major breath test manufacturer, eventually brought their concerns to the National Highway Traffic Safety Administration (NHTSA). The manufacturer specifically noted that police radios were causing major interference by disrupting breath testing. Eventually, changes were made to breathalyzers in order to try to eliminate RFI from police radios. According to a report on breath tests from the National District Attorneys Association (NDAA), that specific issue has been largely resolved. However, other types of more complex radio interference can come from different sources. For example, in the modern world, the majority of people have a smartphone in their pocket. This is still a new phenomenon; just 15 years ago it was not as common for a person to be carrying any type of cell phone, but they can emit radio frequencies that are able to interfere with the results of breath tests. It is possible that your BAC tests are inaccurate due to this and other types of interference.

You Need Legal Protection Against Flawed BAC Test Results

To convict you of a DWI offense, Texas prosecutors are required to prove your guilt beyond a reasonable doubt. Many DWI cases rely heavily on the results of BAC tests. Yet, in some cases, potential radio frequency interference (RFI) undermines the reliability of those BAC test results. Breath test results should always be reviewed to ensure accuracy. If you believe that radio frequency interference has resulted in your BAC tests coming back as a false positive, you should speak to an experienced Austin DWI defense attorney immediately.