BAC Definition Under Texas State Law

The definition of BAC under Texas state law is “blood alcohol concentration,” or the number of grams of alcohol found in a sample of a drunk driving suspect’s blood. The Texas Penal Code (TPC) defines the specific BAC levels that constitute statutory intoxication.

How Does Texas State Law Define BAC or Blood Alcohol Concentration?

Chapter 49 of the TPC defines “alcohol concentration” as the number of alcohol grams contained in a chemical testing specimen of blood, breath, or urine, specifically in the following quantities.

  • 210 liters of breath
  • 100 milliliters of blood
  • 67 milliliters of urine

The statute defines intoxication as “having an alcohol concentration of 0.08 or more.”

We commonly use the term “BAC” interchangeably with the statutory “alcohol concentration” term, as it is most commonly recognized and understood by the public. In this context, it may describe the alcohol concentration in a suspect’s breath or urine as well as blood. You may also see the abbreviation BAC used for the term “blood alcohol content,” again referring to the same basic concept and measurement.

What Determines a Driver’s BAC in Texas?

The factors that influence the level of alcohol in a driver’s bloodstream include the following:

  • What type of alcohol you drank
  • How much alcohol you drank
  • The time period in which you drank
  • Your gender
  • Your age, weight, and health status
  • Whether you ate or drank other substances
  • Whether you are taking medications

The Texas Alcoholic Beverage Commission (TABC) offers an informative, albeit generalized, guideline for how much alcohol consumption over the course of one hour can lead to impairment for men and women.

How Is BAC Calculated in Texas?

A simple calculation to help understand and remember this concept is as follows:

To determine BAC, a testing lab would count the number of parts of alcohol for every 1,000 parts of blood. If an individual had one-part alcohol for every 1,000 parts of blood, they would have a BAC of 0.10.

Because the per se definition of intoxication in Texas is a BAC of 0.08, you would need your chemical test to reflect one-part alcohol for every 800 parts of blood.

How Do Police Measure BAC in Texas?

The way the police will measure your BAC after a traffic stop depends on the type of chemical test they choose.

Breathalyzer Test for BAC 

In Texas, most law enforcement agencies use equipment known as the Intoxilyzer 5000 to measure the alcohol concentration in a breath sample. The Intoxilyzer uses infrared (IR) light to analyze a breath sample. The more light the alcohol in the sample absorbs, the higher the concentration of alcohol.

Blood Test for BAC

The Texas Transportation Code (TTC) outlines some legal aspects of obtaining a blood specimen for BAC testing. However, the sampling and testing protocols are not clearly defined, as they are for breath testing. Generally, as long as the testing lab meets the Texas Code of Criminal Procedure standards and the Department of Public Safety (TxDPS) Crime Lab accreditation requirements, the lab can conduct testing at its discretion.

Urine Test for BAC 

Although the police rarely use urine testing for BAC in Texas, this method does provide another legal avenue for the police to establish intoxication levels. As with blood testing, the statutes do not clearly establish testing procedures for urine samples. Consequently, the testing lab is free to use whatever commonly accepted analysis procedure it chooses.

How Can a Texas BAC Testing Lawyer Help?

For legal issues related to DWI and BAC testing, a lawyer can help in a variety of important ways.

  • Protecting your legal rights
  • Ensuring you understand your options
  • Exploring evidence for potential errors
  • Challenging potentially faulty evidence
  • Building a strong case for your defense

No matter which type of testing the police used to establish your BAC, procedural errors or failure to follow established guidelines and protocols could produce incorrect results.

A variety of factors could affect the results of BAC testing. For example, some foods, beverages, medications, and oral hygiene products can lead to a false positive breathalyzer test. Blood and urine tests can become contaminated during the analysis process or if stored improperly by the lab.

Never assume that chemical testing evidence for BAC guarantees a conviction for drunk driving. By talking to a BAC testing result defense lawyer, you can potentially discover alternatives to pleading guilty to DWI in Texas.

Can I Talk to a BAC Testing Lawyer at No Charge?

The Law Offices of Randall B. Isenberg offers a complimentary case evaluation and consultation for individuals facing DWI and related charges in Texas. Contact us at 214-696-9253 to learn more or to schedule a complimentary case evaluation and consultation with a DWI lawyer.

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