Blood Alcohol Content – DWI in Texas

There are several important factors to understand when researching Blood Alcohol Testing and the impact on DWI in Texas.  The legal blood alcohol level (BAC) in Texas is .08%. If you are under this limit, over the age of 21 and a non-commercial driver you can legally drive and/or operate a vehicle. However, it is easy to reach the legal limit of .08%. You may be wondering what affects your BAC? Is it possible to estimate your own BAC? If so, how do you estimate your own BAC?

What is the legal blood alcohol content limit for driving in Texas?

Blood Alcohol Content Austin Texas DWI

Understanding Blood Alcohol Content

The legal alcohol limit in Texas falls into three categories:

If you are at or over the age of 21 and:

  • A non-commercial driver, the legal alcohol limit is .08%.
  • A commercial driver holding a CDL, the legal alcohol limit is .04% for any vehicle you operate.

If you are under 21:

  • Any breath test that measures any amount of alcohol may result in a driver’s license suspension.

Blood Alcohol Content – Calculating your BAC in Texas

Blood Alcohol Testing is used to determine your Blood Alcohol Content.  You BAC is a formula that is calculated by dividing the number of milliliters of alcohol per 100 milliliters of blood. For most people, 2-3 drinks per hour is all it takes to reach the legal BAC of .08%. If you consume two drinks in an hour you are likely impaired. If you consume three drinks per hour you are likely legally intoxicated. The definition of a drink varies widely. For the purposed of this measurement, one drink is:

  • 1.5 ounces of 80 proof liquor (40% alcohol by volume)
  • 1 12-ounce beer (4.5% alcohol by volume)
  • 1 5-ounce glass of wine (12% alcohol by volume)

Generally speaking, adults over 100 lbs can consume one drink per hour and still drive. It’s important to understand the type of alcohol, volume of alcohol in the drink and rate of drink consumption when deciding how much is too much.

Commercial Drivers and DWI in Texas

Commercial drivers in Texas have a much lower barrier to receiving a DWI for failed Blood Alcohol Testing. If you are a commercial driver and hold a CDL your blood alcohol limit is only .04%. The law is more stringent for commercial drivers due to the nature of vehicles they operate and the threat to passengers and other drivers.

The .04% blood alcohol limit applies at all times for any vehicle you operate. This includes personal vehicles.
Commercial drivers are subject to random BAC tests. Probable cause does not need to be established to conduct a field sobriety test.

DWI laws for Those Under 21 in Texas

It is legal to drink in Texas if you are under 21 and with a parent. However, driving after consuming any alcohol under the age of 21 is illegal. Texas is a zero-tolerance policy for alcohol found in drivers under 21. At a minimum, you will most likely have your license suspended.

What should you do if your blood alcohol content is over .08% and you have been arrested?

Schedule a free consultation with The Hull Firm. We are here to help you avoid harsh sentencing, receiving probation over jail time and having a successful ALR hearing.

How does the State prove my blood alcohol content?

There are two ways the State can test for your blood alcohol content: A trained phlebotomist can take your blood, or you can provide a breath sample. These Blood Alcohol Testing samples are analyzed for your blood alcohol content.

Can I refuse to provide a breath and/or blood sample?


Should I refuse to provide a breath and/or blood sample?

You have the right to refuse to provide a breath or blood sample. However, it is always important to be polite and courteous to the officer. Something to keep in mind: Providing a breath or blood sample gives the State more evidence supporting their claim that you were driving while intoxicated.

Can my blood be taken if I refuse?

Yes. The 4th Amendment of the United States Constitution protects you against illegal search and seizure. This means that the officer will have to get a warrant to take your blood if you do not volunteer a sample. Once the officer has a warrant, they can take your blood without your consent.

What does “no refusal weekend” mean?

During holidays and certain weekends that have major events going on (i.e. Memorial Day, Fourth of July, ACL Festival, etc.), the City can enact a “no refusal” policy. This means that if you are suspected of DWI by an officer, a Judge is available to immediately sign a warrant to obtain your blood, without your consent.

What are mental and physical faculties?

Examples of mental faculties are: Did you know where you were when you got pulled over? Did you know approximately what time it was? Were you making sense? Were you obviously lying (changing your story)? Did you have slurred speech?
Physical faculties are tested with the Standardized Field Sobriety Tests (SFST’s).

What are SFST’s?

Officers are trained to administer Standardized Field Sobriety Tests in order to test your physical and mental faculties. SFST’s are not a substitute for Blood Alcohol Testing.  These tests require you to pay attention, follow directions, multitask, and display balance. These tests are not pass/fail. The officers use their observations to determine if, as a whole, they believe that you are without your mental or physical faculties.

Should I refuse SFST’s?

You have the right to refuse the SFST. However, it is always important to be polite and courteous to the officer. Again, keep in mind that performing the SFST gives the State more evidence supporting their claim that you were driving while intoxicated.

Will I have to get a breathalyzer?

It depends. If Blood Alcohol Testing reveals your BAC is greater than 0.15, the court may automatically require that you get an ignition interlock device (IID) installed in your car. The judge may consider other factors when deciding if an IID should be a condition of your bond. For example: if this is your 2nd DWI, if there was an accident involved, or the circumstances of your arrest. The judge will consider these things and may require you to get an IID installed after you are released from jail.

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