Blood Alcohol Concentration (BAC) measures the amount of alcohol in your bloodstream. Expressed as a percentage, it represents grams of alcohol per 100 milliliters of blood. For instance, a BAC of 0.08% indicates that there are 0.08 grams of alcohol per 100 milliliters of blood. In Texas, like many states, driving with a BAC of 0.08% or higher is illegal.
The Science of Alcohol Absorption and Metabolism
Alcohol is absorbed into the bloodstream primarily through the stomach and small intestine. Once in the bloodstream, it’s carried throughout the body, including the brain, which is why it affects behavior and motor skills. Several factors influence how quickly alcohol is absorbed and metabolized, including:
- Body weight and composition: More body fat slows the absorption of alcohol.
- Food intake: Eating food can slow the absorption rate.
- Gender: Generally, women have a higher BAC than men after consuming the same amount of alcohol due to differences in body composition and hormonal factors.
- Rate of consumption: Drinking quickly results in higher BAC.
- Type of alcohol: Higher concentration drinks result in higher BAC.
More Information: High BAC DWI Defense
Methods of BAC Testing
Breath Testing
Breathalyzers are the most common method used by law enforcement to measure BAC. These devices estimate BAC based on the alcohol content in your breath. The science behind this involves the exchange of alcohol between the blood and breath in the lungs. When you exhale, the alcohol in your blood is expelled at a predictable rate.
- Infrared Spectroscopy: Some breathalyzers use infrared light to detect alcohol molecules in the breath. The light absorption by alcohol molecules provides a measure of BAC.
- Fuel Cell Technology: Others use fuel cells that react with alcohol to produce an electric current, which is then converted into a BAC reading.
Despite their popularity, breath tests have limitations. Factors like body temperature, the presence of other chemicals, and even certain diets can affect the readings.
Blood Testing
Blood tests are considered the most accurate method for measuring BAC. Blood samples are analyzed using techniques like gas chromatography, which separates and quantifies alcohol content. This method provides a precise BAC measurement, but it’s invasive and typically used in more formal or contested situations.
Urine Testing
Urine tests measure the presence of alcohol metabolites rather than alcohol itself. This method is less accurate than blood or breath testing and is typically used when the other methods aren’t available. It’s more reflective of past alcohol consumption rather than current impairment.
Saliva Testing
Saliva tests, though less common, measure alcohol presence in the saliva. Like urine tests, they are less precise and not commonly used for legal purposes.
Texas Law & Suspected Drunk Drivers
Under the Texas Penal Code § 49.04, a person commits an offense if they operate a motor vehicle in a public place while intoxicated. Intoxication is defined as:
- Not having the normal use of mental or physical faculties due to alcohol, drugs, or a combination.
- Having a BAC of 0.08% or more.
If you’re pulled over under suspicion of DWI, you may be asked to perform field sobriety tests and provide a breath or blood sample. Refusing to provide a sample can result in automatic license suspension under Texas’s implied consent law (Texas Transportation Code § 724.011).
Challenging BAC Test Results
As experienced Texas DWI attorneys, Tad Nelson and Amber Spurlock, both ACS/CHAL Lawyer-Scientists, understand the complexities of challenging BAC test results. Here’s how we approach these challenges:
Calibration and Maintenance of Testing Equipment
Breathalyzers must be regularly calibrated and maintained to ensure accuracy. If we find evidence that the device used wasn’t properly maintained, we can challenge the validity of the test results.
Officer Training and Protocol
Law enforcement officers must follow strict protocols when administering BAC tests. Any deviation from these protocols can result in inaccurate readings. We scrutinize the officer’s training records and the procedures followed during your DWI arrest.
Physiological Factors
Individual physiological factors, such as medical conditions or unique body chemistry, can affect BAC readings. Conditions like GERD (Gastroesophageal Reflux Disease) can cause alcohol to be present in the mouth, leading to falsely high breathalyzer readings.
External Factors
External factors, such as the environment in which the test was conducted or the presence of interfering substances, can also impact the results. For instance, certain mouthwashes or medications contain alcohol and can skew breath test results.
The Constitution of the United States & You
The Fourth Amendment to the Constitution of the United States protects against unreasonable searches and seizures, which can be highly relevant in DWI cases.
A BAC test is considered a search. Therefore, law enforcement must have probable cause to administer a BAC test. If we determine that the traffic stop or subsequent search violated your Fourth Amendment rights, we can move to suppress the evidence. If this happens, it’s good for your case.
Texas Code of Criminal Procedure
The Texas Code of Criminal Procedure outlines the legal processes and rights afforded to individuals accused of crimes, including DWI.
Under Article 38.23, any evidence obtained in violation of the Constitution or laws of Texas or the United States must be excluded. This exclusionary rule is a critical tool in DWI defense, as it allows us to challenge improperly obtained BAC test results.
Local News and Public Perception
Some DWI cases can attract significant media attention, especially if they involve accidents or injuries. Public perception can influence the legal process, but remember that every defendant is presumed innocent until proven guilty. At Tad Nelson & Associates, we know how to handle public opinion, ensuring that media coverage doesn’t impact the fairness of your trial.
Facing DWI Charges With Blood Evidence?
Call Tad Nelson & Associates Today!
Fighting a DWI case with BAC testing evidence is a complex interplay of biological, technological, and legal factors. At Tad Nelson & Associates, our deep understanding of these elements, coupled with our commitment to your defense, ensures that we leave no stone unturned in protecting your rights.
If you’re facing DWI charges in Houston or the Greater Houston region, call us at 281-502-2122. Schedule your personal consultation with Houston DWI Lawyers Tad & Amber today. We’re here to fight for you.
