How To Challenge BAC Chemical Test Results In Texas DWI Cases

How To Challenge BAC Chemical Test Results In Texas DWI Cases

A DWI (Driving While Intoxicated) criminal conviction will have life-changing consequences with significant legal and financial impacts. For many clients, the crux of the case is the result of a blood alcohol concentration (BAC) test, which prosecutors often view as irrefutable evidence. However, BAC chemical test results are not flawless. At Mark Diaz & Associates, our Galveston DWI defense attorneys understand the science behind BAC testing and the potential errors that can arise, leading to false or misleading results.

As Texas DWI lawyers, we know the importance of questioning every detail in a case to defend our client’s rights. We will now explain key strategies to challenge BAC chemical test results, drawing from Texas DWI laws and statutes. If you’re facing a DWI charge, this information can help you understand how we approach these cases to protect your future.

Understanding BAC Chemical Testing In Texas

In Texas, law enforcement agencies may use various chemical tests to determine a person’s BAC. These tests include breath tests (using a machine such as the Intoxilyzer 9000), blood tests, and, occasionally, urine tests. The legal BAC limit for most drivers is 0.08%, but for drivers under 21, Texas enforces a zero-tolerance policy. While these tests seem straightforward, the results are only as reliable as the procedures used to administer them. Our job as DWI lawyers is to examine each step of the BAC testing process to identify any flaws that could cast doubt on the accuracy of the results.

Texas Law And BAC Test Admissibility

In Texas, BAC test results must meet certain legal requirements to be admissible in court. According to the Texas Penal Code § 49.04, a DWI conviction hinges on proving that a person’s BAC exceeded the legal limit or that they were otherwise impaired. For the prosecution to be allowed to admit BAC results as evidence in your criminal trial, the prosecution must show that the testing process adhered to Texas Department of Public Safety (DPS) standards. If there are deviations in the procedures, we can file motions to suppress the evidence, which could weaken the state’s case against you.

Common Issues With BAC Breath Testing Machines

Breath-testing machines are often viewed as reliable. However, several factors can affect their accuracy. We examine these factors in each case, looking for:

• Calibration Errors: Texas requires regular calibration of breath-testing machines to ensure accuracy. If a machine isn’t calibrated correctly, it may produce inaccurate readings. We review maintenance records to determine if there were lapses in calibration.
• Residual Mouth Alcohol: Certain substances, such as mouthwash or medications, can cause residual alcohol to remain in a person’s mouth, leading to inflated BAC results. Texas law requires officers to observe the individual for a minimum period (usually 15 minutes) before administering the test, allowing any residual alcohol to dissipate. We verify whether this observation period was followed.
• Health Conditions and Breathing Patterns: Conditions like acid reflux, diabetes, or asthma can affect breath test results. Additionally, deep or shallow breathing can alter the BAC reading. We often consult medical experts to evaluate whether a client’s health condition could have impacted the results.

Problems With Blood Testing In Texas DWI Cases

Blood tests are generally more accurate than breath tests but are not immune to errors. When evaluating blood test results, we consider the following factors:

• Chain of Custody Issues: For blood test evidence to hold up in court, there must be an unbroken chain of custody from the time the sample was drawn to its analysis. If there’s a gap or irregularity in handling, we may challenge the test’s reliability.
• Contamination: Blood samples could become contaminated if not properly collected or stored. If the sample was not preserved correctly, the alcohol content could increase over time, leading to artificially high BAC readings.
• Testing Procedures: In Texas, blood tests must follow strict procedural guidelines. These guidelines include sterilizing the skin with non-alcohol-based swabs before drawing blood. Using an alcohol-based swab can cause contamination and potentially lead to a false positive. We scrutinize every step taken during the blood draw and handling process to identify any procedural lapses.

Challenging The Timing Of BAC Testing

In DWI cases, timing is crucial. A driver’s BAC can fluctuate after drinking, and Texas law recognizes that BAC levels change over time. Known as “retrograde extrapolation,” this principle considers how alcohol is absorbed and metabolized by the body. If significant time elapsed between the arrest and the BAC test, the results might not accurately reflect the BAC at the time of driving. We frequently work with experts to analyze the timing of BAC testing in our cases, arguing that the results do not directly correlate with our client’s condition while driving.

Legal Defenses To BAC Test Results In Texas

Several legal defenses may apply to challenge BAC test results in Texas, including:

• Constitutional Violations: If an officer did not have probable cause to conduct a BAC test, we may argue that your Fourth Amendment rights were violated. An illegal stop or lack of probable cause can lead to the suppression of evidence.
• Lack of Informed Consent: Texas follows an “implied consent” law, meaning that drivers implicitly agree to BAC testing if arrested for a DWI. However, officers must inform you of the consequences of refusal. If they failed to do so, we may argue that you did not give informed consent.
• Invalid Test Administration: Texas requires specific protocols for BAC testing. If we identify any procedural errors, such as improper storage or handling, we may file a motion to exclude the test results from evidence.

Steps We Take To Challenge BAC Test Results

At Mark Diaz & Associates, we take a proactive approach to challenging BAC test results. Here’s a look at the steps we typically follow:

1. Reviewing the Arrest and Testing Procedures: We carefully review the police report, looking for any procedural errors during the arrest and BAC testing.
2. Obtaining Maintenance and Calibration Records: For breathalyzer tests, we check the machine’s maintenance and calibration history.
3. Consulting Experts: In cases involving health conditions or timing issues, we consult with medical and forensic experts to understand how these factors might have impacted the BAC results.
4. Filing Motions to Suppress Evidence: If we identify issues that undermine the reliability of the BAC test, we file motions to suppress the results from being used as evidence.

Our goal in every DWI case is to reduce or dismiss the charges by challenging every piece of evidence that can be called into question.

Breathalyzer Test FAQs

How Accurate Are Breathalyzer Tests In Texas DWI Cases?

Breathalyzer tests are generally accurate when maintained and calibrated correctly, but they are not infallible. Several factors, such as machine calibration errors, medical conditions, and the presence of certain substances in the mouth, can impact the accuracy of breath tests. Texas law requires breathalyzers to be calibrated at regular intervals to ensure reliability. When defending a client, we obtain the calibration and maintenance records for the breathalyzer to verify whether it was in proper working order at the time of testing.

Can A Health Condition Affect BAC Test Results?

Yes, certain health conditions can interfere with BAC results. For example, individuals with acid reflux may have residual alcohol in their esophagus, leading to falsely elevated BAC levels in a breath test. Diabetic individuals can produce acetone, which breathalyzers may mistake for alcohol. We consult with medical experts to determine whether a health condition could have influenced the results and challenge the BAC findings if applicable.

What Happens If The Police Don’t Follow The Correct Procedures For A BAC Test?

If the police fail to follow proper procedures, we may file a motion to suppress the test results. Texas law mandates specific guidelines for administering BAC tests, including the observation period and chain of custody for blood samples. Any deviation from these guidelines can affect the admissibility of the test results. Suppression of the BAC evidence could weaken the prosecution’s case, potentially leading to a reduction or dismissal of charges.

How Does Texas Law Handle BAC Test Refusals?

Texas operates under an “implied consent” law, meaning that by driving, you consent to BAC testing if arrested for DWI. However, you have the right to refuse testing, although it comes with penalties, such as automatic license suspension. In many cases, a refusal can still be used as evidence against you in court. We often address BAC refusals by questioning the officer’s actions during the arrest and ensuring they informed you of the consequences before requesting the test.

Can A Blood Test Result Be Challenged In Texas?

Yes, blood test results can be challenged on several grounds. Issues with chain of custody, contamination, improper handling, or use of alcohol-based swabs can all affect the accuracy of blood test results. In many cases, we scrutinize the entire process, from collection to analysis, to identify potential issues that could make the test results unreliable.

Call Our Galveston DWI Lawyer For Your Free Consultation

If you’re facing DWI charges based on BAC test results, it’s critical to have a legal team that understands how to challenge these tests effectively. At Mark Diaz & Associates, we are committed to protecting your rights and seeking the best possible outcome for your case. We invite you to reach out to our experienced Galveston DWI lawyers for a free consultation.

Contact our Galveston DWI lawyer at Mark Diaz & Associates by calling 409-515-6170 to receive your free consultation and to discuss how we can help with your defense. Our firm serves clients throughout Galveston, Chambers, and Harris Counties, and we’re here to guide you through each step of the process.