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Challenging Chemical Tests in a Parker County DWI

Thumbnail image for Thumbnail image for romberg.jpegPartially due to the stern warnings about mandatory drivers' license suspension and the use of refusal information in court, about 75 percent of the people who are arrested for DWI submit to a chemical test. Many others probably do not fully understand that they have a right to refuse the test, and they do not understand how much chemical tests increase conviction rates.

In Texas, if the chemical test reveals a Blood Alcohol Content level above the legal limit, the defendant is guilty as a matter of law. However, a Weatherford criminal defense attorney may be able to successfully challenge chemical test results. That's especially true if, as is usually the case, the defendant blew into a Breathalyzer and had a BAC lower than 1.0 or 1.1.

Beating the Breathalyzer

Attentive readers probably noticed that the Breathalyzer measures breath alcohol level and not blood alcohol level, which is the legal standard. Instead, the Breathalyzer estimates BAC level based on the breath alcohol content. That extra step causes a larger margin of error, especially if there is evidence of:

  • Mouth Alcohol: A single burp or belch in the fifteen minutes before the test floods the mouth with ethanol particles. These particles artificially raise the breath alcohol level, which skews the BAC estimate.

  • Unabsorbed Alcohol: Basically the same result occurs if the defendant had been drinking in the hour or so before the test. Generally, alcohol goes from the stomach through the liver and into the blood, instead of directly from stomach to blood. The slower absorption process means that the BAC level may be lower than the Breathalyzer estimate.

  • Acetone Particles: Many people, mostly smokers and diabetics, have high acetone levels in their bloodstreams. A simple pretrial blood test can establish the elevated level. Breathalyzers register acetone as ethanol. So, once again, the BAC estimate may be artificially high.

To drive home these flaws with the Parker County jury, many attorneys partner with professional chemists. These highly-educated professionals explain these flaws to the jury, and these people are much more persuasive than Breathalyzer techs.

Additionally, expert witnesses can reinforce the ancient technology which the Breathalyzer uses. The first such machines appeared in the late 1940s. Modern Breathalyzers are smaller and have more bells and whistles, but under the hood, they are basically the same.

Refuting Blood Test Results

Because it directly measures blood alcohol level, DWI blood tests are more reliable than Breathalyzer tests. But they are not 100 percent accurate all the time. Additionally, since the Supreme Court ruled that police officers need search warrants to draw blood, not many DWI cases involve blood tests.

The blood sample may be inaccurate. Since blood tests preserve the sample, an attorney can request a re-test. Subsequent tests at sophisticated laboratories often yield different results than the ones police technicians find.

DWI chemical tests are not totally infallible. For a free consultation with an experienced criminal defense attorney in Weatherford, contact Herreth Law. We routinely handle matters in Parker County and nearby jurisdictions.

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