DWI Chemical Testing in Texas

Under Texas law, driving while intoxicated (DWI) is a misdemeanor. Intoxication is generally shown through chemical testing of the driver's breath, blood, or urine. The prosecutor may use these chemical tests to show that the driver's blood alcohol concentration (BAC) is 0.08% or higher or showing the presence of drugs and/or alcohol in the body.

Unfortunately for drivers, these chemical tests are not always accurate. Test results can be tainted by other foods, medicines, or health issues. Testing can also be contaminated by improper handling of the chemical testing devices or samples. If you were arrested on suspicion of a DWI, you may be able to challenge the chemical test results to win your case or have your charges reduced. Talk to your experienced Odessa DWI defense lawyer to understand your rights and defenses.

Texas DWI Chemical Tests

Chemical testing in Texas includes breath, blood, or urine tests. In most cases, if the driver is suspected of driving while intoxicated by alcohol, police will use a breath testing device. If the driver is suspected of driving while intoxicated by drugs or a combination of drugs and alcohol, law enforcement will generally use a blood or urine test.

Alcohol concentration is measured by the following number of grams of alcohol per tested unit:

  • 210 liters of breath;
  • 100 milliliters of blood; or
  • 67 milliliters of urine.

A BAC of 0.08% or higher means the driver is per se intoxicated, even if the driver appeared to be driving fine. However, a higher BAC can result in increased penalties. Driving with a BAC of 0.15% or higher is a Class A misdemeanor.

If your BAC is below 0.08%, you may still face DWI charges. For a DWI with an alcohol level below the legal limit, the prosecutor will have to prove that you did not have the normal use of mental or physical faculties by reason of alcohol, drugs, or a combination into the body.

Problems with Chemical Testing After a DWI

There can be a lot of problems with chemical testing that result in incorrect measurements. This can increase or decrease the driver's apparent BAC level, or falsely test positive for certain drugs. Chemical testing problems include the following:

  • Operator error
  • Machine error
  • Testing errors
  • Mixing up samples
  • Certain foods or medicines
  • Improper calibration
  • Failing to properly clean the device
  • Failing to properly observe the test subject
  • Intentionally manipulating the tests, or
  • Health issues.

Breath testing devices may show the presence of alcohol from sources other than alcoholic beverages. This can include mouthwash, cough drops, breath mints, chewing gum, or medication. Alcohol levels also change over time and can be higher or lower at the time of testing compared to the time when the driver was behind the wheel.

Additionally, if law enforcement does not follow the requirements for ensuring accurate chemical testing (observation times, regular calibration, handling chemical test samples), the test results can be compromised. Your Texas DWI lawyer can investigate the chemical testing procedures, equipment, and chain of evidence to suppress to keep chemical test results or challenge the accuracy of the results in court.  

Refusing a Chemical Test in Texas

Under Texas Transportation Code § 724.011, drivers in Texas have given their implied consent to chemical testing by operating a motor vehicle in public. This generally means that the law considers you to have consented to a chemical test just by driving in Texas. Under Texas' “implied consent” laws, you face consequences for refusing a breath, blood, or urine test after a DWI arrest.

The penalties for refusing a chemical test include a suspended license. The license suspension period depends on how many times the driver has refused to give a chemical sample, as follows: 

Chemical Test Refusal

License Suspension Period

1st Refusal

180 Days

2nd Refusal (Within 10 Years)

2 Years

3rd or Subsequent Refusal (Within 10 Years)

2 Years

If your license is administratively suspended for a refusing a chemical test, you may be able to apply for an occupational license. This generally limits the driver to operate a vehicle in connection with work, school, or essential household duties.

Odessa DWI Lawyer

An experienced DWI defense attorney can help you build a defense that gives you the best shot at a favorable outcome, including challenging DWI chemical tests. If you've been charged with a DWI in Odessa, Texas, the Law Office of E. Jason Leach, PLLC is here to fight for you. E. Jason Leach is a board-certified criminal defense attorney that has dedicated his law practice to defending the accused. To set up a free consultation contact the Law Office of E. Jason Leach today at (432) 552-7000.