woman being pulled over for dwi

Why You Should Blow Instead of Giving Blood in a DWI Arrest

By Jose Ceja
Managing Attorney

If you are arrested for DWI anywhere in the Greater Houston area, it is very likely that you will give a breath or blood sample, either voluntarily or not. After you are placed under arrest for DWI, an officer will typically ask you to give a breath or blood sample. What should you do? Consent to breath or exercise your right to refuse? This article discusses why it is almost always in your best interest to give a breath sample if you are arrested for DWI in the Greater Houston area. 

You should understand that if you refuse a breath test in Houston and many surrounding counties, law enforcement will contact the Harris County District Attorney’s Office and a warrant will be drafted for your blood. This is what is referred to as the “no refusal” policy which is in effect for DWI cases in Houston.

As we have noted in other posts, at least in Houston, it is probably in your best interest to submit to a breath test if you are arrested for DWI for several reasons. First, the police in Houston (and most surrounding counties) will almost certainly obtain a warrant for your blood in the event of your refusal. Blood is more accurate than breath, so one consequence of a refusal will be that the police will end up with more accurate and powerful evidence to use against you in a possible DWI trial. Additionally, a refusal is subject to a longer potential driver’s license suspension. Finally, it is always better for your attorney to be able to say that you were cooperative during your DWI investigation and had nothing to hide. 

But why is breath testing inferior to blood? The science behind breath testing is known as infrared spectroscopy. Basically, the breath testing device emits a certain type of infrared radiation that is partially absorbed by the passing breath. The reduction of the intensity of the radiation due to the absorption is measured and translated to an estimate of the amount of alcohol in the breath sample and a suspect’s blood. It is well-known that this method is much less accurate than blood testing.

The breath test machine – currently a device known as the Intoxilyzer 9000 in Texas – has several quirks that should tell you how questionable the technology is. One such quirk is known as the “.02 agreement.” If you are asked to give breath sample, you will blow twice. As you may know, in Texas, the legal limit is .08. Amazingly, the two samples do not have to agree for the breath test to be considered accurate. In fact, the second number can be as much as .02 higher or lower than your first result. In other words, if you blew a .08, the other result can be as high as .10 or as low as .06 to be considered accurate – a difference of 25 percent! To put this in perspective, this would be like taking your temperature twice, and the device insisting that it gives accurate readings, even if the first reading is 100 degrees and the next reading is 125 degrees. 

Another issue with breath testing in DWI cases is that it can be affected by mouth alcohol. A simple burp can significantly increase the result of the breath test. That is why breath testing regulations require a 15-minute observation period prior to taking the breath test to ensure that a person doesn’t burp. But unless we are talking about a noticeably large belch, many burps simply are not noticed. 

Amazingly, the Intoxilyzer 9000 is potentially subject to having its results be affected by radio frequency interference from police scanners, radio, or Wi-Fi. Many DWI attorneys have noted that this is one of the shortcomings of the machine and that proper safeguards are not in place to prevent such errors. There are also less common, but equally problematic possibilities for error, such as gastric esophageal reflux disease (GERD), which can falsely elevate a breath test score. 

Blood testing, on the other hand, is regarded as far more reliable by jurors. Although the average juror in a DWI case will know virtually nothing about the science behind any type of alcohol test, most jurors will have a sense that blood tests are commonly used everywhere. Most jurors in DWI trials have had drawn and never had any reason to distrust the result. On the other hand, a DWI juror will have the impression that breath testing is really only used by the police in the context of DWI investigations, and be more likely to accept that breath tests are more prone to error. 

So if you are arrested for DWI in the Greater Houston area, and are asked to give a breath sample, you will be essentially providing the State with more powerful and reliable evidence if you refuse since it is very likely the State will obtain a warrant for your blood. Additionally, a refusal will subject you to a 180-day suspension, instead of a 90-day suspension if you take a breath test and are over the legal limit (a so-called “failure”).

But whether you blow or give blood, this article should make you aware of the fact that alcohol testing is complex and requires specialized training. Attorney Jose Ceja has spent hundreds of hours studying the science behind both breath and blood testing and is an excellent choice to handle your DWI case. If you are arrested for DWI anywhere in the Greater Houston area, Mr. Ceja is an excellent choice.  

About the Author
Jose Ceja is the managing attorney of Ceja Law Firm. He has practiced law since 2007 and has devoted his career to the practice of criminal law. Mr. Ceja began his legal career as a felony drug prosecutor, where he prosecuted drug, gang, and violent offenses. Mr. Ceja has first or second chaired almost 100 trials, including murders, drug cases, DWIs, and assaults. In his career as a defense attorney, he has regularly obtained dismissals, not guilty verdicts, and grand jury “no bills” in a wide variety of cases.
Posted in DWI