How to Challenge the Blood Alcohol Test

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Nobody is perfect...not even police officers. Human error can give incorrect results in any sobriety test, including blood draws. A skilled DWI attorney should know how to challenge the blood alcohol test so you can receive a "not guilty" verdict.

Texas has approved two separate chemical tests to determine a person’s alcohol level: the breath chemical test and the blood alcohol test (BAC test). Urine tests are sometimes used but, since urine is basically the body’s garbage, these tests only prove that a certain substance was consumed, not that it is actively impairing someone to the amount required for a conviction. While there are plenty of reasons why breath and urine tests can be challenged in your DWI case, this article will focus on how to challenge the blood alcohol test during your DWI trial.


When Blood Alcohol Tests are Administered

Most states, including Texas, have Implied Consent Laws. In layman’s terms, if you are driving a car on a public roadway, it is assumed you have given consent to a chemical test if you are suspected of driving under the influence of alcohol or other intoxicating substance. As the driver, you have the right to refuse the test, but refusing can result in an administrative suspension of your driving privileges. The arresting officer has the choice of whether to administer a breath chemical test or a blood test. However, the officer must follow certain guidelines established by Texas Statutes.

In Texas, if your arrest occurs in a county with a “No Refusal” policy, your refusal will not be honored. The police officer will simply get a warrant and obtain a forced blood draw. If the driver is unconscious and unable to give consent to a chemical test, the driver’s consent is considered implied, and the police officer can order a blood test to be administered. If the driver refuses, the police officer can obtain a search warrant for the driver’s blood.


How Blood Alcohol Tests are Administered

If a blood alcohol test is required or consented to, the officer will use a blood kit to obtain the blood. This is a standard blood withdrawal kit that is completely self-contained. The officer can only direct a physician, qualified technician, chemist, registered professional nurse, or licensed vocational nurse to withdraw the blood samples in the officer’s presence.

Most “No Refusal” programs have jail nurses on standby to draw blood. Some Texas police department are training the arresting officers to become certified to draw blood as well.


How to Challenge the Blood Alcohol Test

Because of the large amount of human intervention needed to draw, preserve, transport, and test blood samples, there is also a large opportunity for your blood sample to become compromised. Fortunately, this high margin of error makes it possible to challenge the results in court when it is time for your trial.

The first point of contact comes when your blood samples are given to the police officer, who will seal them, repackage the vials into the blood kit, and take the kit to the proper laboratory for analysis. The arresting officer is responsible for preserving the samples until they are delivered to the state-approved forensic lab for testing. If the officer is not able to deliver the blood kit to the lab within 24 hours, he must refrigerate it.

Failing to refrigerate a blood sample is crucial, as blood can ferment if left exposed to heat (such as our hot Texas summers provide) for too long. If fermentation occurs, it will cause an increased blood alcohol level in the blood sample. Increased blood alcohol levels can also result if the blood sample has been contaminated. If your attorney can prove that any of these conditions might have taken place, challenging the blood alcohol test is easy.

If a police officer takes a specimen from a defendant, the defendant can have an independent laboratory conduct a separate independent analysis. This independent test allows the opportunity to double-check and confirm the work of the State’s laboratory. However, if there is an increased blood level due to human error in procedure (such as not refrigerating a sample right away), the error likely affected all the samples, and an independent test will show the same (incorrect) results. Interestingly, there is no sanction against the State if you are not allowed to obtain an independent sample because you are locked up.

Although it’s been simplified here, the process of testing the alcohol level of blood is complex and often times—because of machine and/or human error—it is possible for blood alcohol tests to report inaccurate results.


How to Estimate Your Blood Alcohol Level

You can estimate the percent of alcohol in your blood by the number of drinks consumed in relation to body weight. You should remember, this is just an estimate. Many factors such as food consumption, prior exposure to alcohol, medical conditions, gender biases, and time of consumption can change the calculations up or down.


A blood alcohol test result over the legal limit, even a high result, is not the nail in the coffin. Skilled attorneys who understand the complexities of how blood alcohol testing works should know how to challenge the blood alcohol test. If a suppression challenge is successful, the blood result will not be admitted and the jury will never know a blood sample was withdrawn.




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