DWI Cases Involving Blood Alcohol Test Errors | Texas

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DWI Cases Involving Blood Alcohol Test Errors

 Posted on July 27,2022 in DWI

TX defense lawyerA key element of any driving while intoxicated (DWI) case is the driver’s blood alcohol level. In Texas, a driver is considered intoxicated if his or her blood alcohol concentration (BAC) is 0.08 percent or higher. While a BAC over the legal limit is not always required to secure a DWI conviction, a driver’s blood alcohol level inevitably plays a major role in a DWI case.

BAC is often determined using a breath test or blood test. However, these tests are not infallible. Multiple issues can occur during testing that invalidate test results. This blog will describe common issues with blood alcohol tests that can be used to defend against DWI charges.

Blood Alcohol Test Results May Be Incorrect

Blood tests are generally believed to be the most accurate way to assess a person’s level of alcohol intoxication. However, these tests must be prepared, administered, and analyzed correctly to yield accurate results.

Common problems with blood tests that can lead to incorrect results include:

  • Timing issues – A person’s blood alcohol concentration changes over time. When someone drinks alcohol, his or her BAC rises slowly over time. If a blood sample is taken long after a DWI arrest, it may be much higher than it was when the person was driving. It is possible for a driver’s BAC is under the legal limit while they are driving but over the legal limit when they are subjected to a blood test.
  • Contamination – Usually, when someone gets their blood drawn, the medical provider cleans the skin with an alcohol wipe before inserting the needle. However, if an alcohol wipe is used before a blood alcohol test, this can contaminate the blood sample leading to a higher BAC result.
  • Improper storage – Blood samples must be stored properly. If blood is not stored properly it can ferment, increasing the BAC level. Improper sealing of the sample can allow bacteria to contaminate the sample.
  • Incorrect amount of additional chemicals – Chemicals like sodium fluoride and potassium oxalate are added to blood samples to preserve the sample and keep the blood from clotting. Adding too much or too little of these chemicals can affect the test results.
  • Unqualified person administered the test – Only certain people are qualified to conduct a blood test for the purpose of determining blood alcohol concentration.

Contact a Floresville Criminal Defense Lawyer

If you or a loved one were accused of drunk driving, contact our Wilson County DWI defense attorneys for help. Call our office at 830-769-1010 for a free, confidential initial consultation.



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