Texas DWI Blood Testing Isn’t Always Accurate

When a person is arrested for a DWI in Texas, there is an “implied consent” statute (TRC Sec. 724.011) that says the driver implies consent to having her breath tested or blood drawn to determine blood alcohol concentration. The law does allow a driver to refuse to have a DWI blood test if there was no accident, but that refusal can come with serious penalties, including suspension of a driver’s license. If you had your blood tested after being stopped for a DWI, the blood sample may have been tainted and you might be able to argue that the test results should be thrown out.

There are many different reasons that a blood sample can be inaccurate. In some cases, problems may have occurred at the time of the blood test, such as sample contamination. In other cases, the blood sample may have been tainted later on through improper storage, for instance. The National Highway Traffic Safety Administration (NHTSA) lists some of the ways in which DWI and DUI blood test samples can be inaccurate, and we would like to go through some of those defenses with you.

Contamination of the Blood Sample

While blood testing frequently is more accurate than breathalyzer test results for determining an individual’s blood alcohol concentration, there are nonetheless many ways in which blood test samples can also be inaccurate. One of those ways involves situations where the blood test was contaminated. How does a blood test get contaminated? Some examples include the following:

In one recent case, a plaintiff argued that the size of the needle used to draw blood led to clotting. Since the amount of blood needed to determine a BAC does not require using the entire blood sample taken from the individual, a sample that includes a clot can lead to an inaccurate blood alcohol concentration reading.

To be clear, errors such as the ones mentioned above occur at the time of the blood test, and they can lead to falsely high BACs. A defendant may be able to argue that the blood sample was contaminated at the time it was taken and therefore is not reliable evidence in a Texas DWI case.

Blood Sample Was Stored Improperly

Sometimes a blood sample is taken properly—and is not contaminated at the time the sample is taken—but the blood sample becomes unreliable due to improper storage. When a blood sample is not stored properly, blood fermentation may occur. Blood that is not stored at a proper temperature or that is not analyzed in a timely manner can become fermented. This refers to a process in which yeast begins to grow and emit alcohol into the blood sample, leading to a higher BAC reading than at the time the sample originally was taken. If you believe your blood sample was contaminated or was stored improperly, an Austin DWI defense attorney can help with your defense.