How A Criminal Defense Lawyer Challenges Breath And Blood Tests In Galveston DWIs
How A Criminal Defense Lawyer Challenges Breath And Blood Tests In Galveston DWIs
A DWI arrest in Galveston often hinges on breath or blood test results. Many assume a reading over 0.08 ends the case, but Texas law requires strict adherence to constitutional, scientific, and technical standards. If law enforcement fails to follow these requirements, the evidence may become unreliable or inadmissible.
We represent clients charged with DWI in Galveston and Houston, regularly challenging breath and blood tests under Texas law. The State must prove intoxication beyond a reasonable doubt, regardless of test results. Below, we outline how these tests are challenged in court and the legal protections available.
Understanding Texas DWI Law And Chemical Testing
Under Texas Penal Code § 49.04, a person commits Driving While Intoxicated if they operate a motor vehicle in a public place while intoxicated. The statute defines intoxication in two ways:
- Not having the normal use of mental or physical faculties due to alcohol or drugs; or
- Having an alcohol concentration of 0.08 or more.
The second definition is often called the “per se” theory. Breath and blood tests are used to support that theory. However, the State must also comply with Texas Transportation Code Chapter 724, which governs implied consent, license suspension procedures, and the legal framework for obtaining specimens.
Testing is not automatic. It must comply with the Fourth Amendment’s constitutional protections. If police obtain a specimen without proper consent or a valid warrant, the evidence may be suppressed.
Challenging The Legality Of The Traffic Stop
Every DWI case begins with a stop. If the officer lacked reasonable suspicion to pull the vehicle over, everything that followed may be invalid.
Officers often claim:
- Failure to maintain a single lane
- Speeding
- An anonymous tip
- Minor equipment violations
We review dashcam and bodycam footage to ensure the stop was justified by specific, articulable facts. Vague claims, such as the driver “looked suspicious,” are insufficient. If the stop was unlawful, we move to suppress all subsequent evidence, including breath and blood test results.
Attacking The Arrest And Probable Cause
Even if the stop was lawful, the officer must establish probable cause before requesting a specimen. Indicators like red eyes, alcohol odor, or slurred speech are subjective.
We scrutinize:
- Field sobriety test instructions
- Officer training and certification
- Whether tests were administered on uneven surfaces
- Weather conditions and lighting
If probable cause was lacking, any subsequent chemical test may be excluded.
Breath Test Challenges In Galveston DWIs
Breath tests in Galveston County are typically conducted using the Intoxilyzer 9000. These machines are regulated by the Texas Department of Public Safety. However, they are not infallible.
Machine Calibration And Maintenance Issues
Breath testing devices must be properly maintained and regularly calibrated. Maintenance logs often reveal gaps, errors, or overdue inspections. If the machine is not operating within the required standards, the result may be unreliable.
Operator Certification Problems
Only certified operators may administer breath tests. If the officer’s certification lapsed or procedures were not followed precisely, the results can be challenged in court.
Observation Period Violations
Texas regulations require a continuous observation period before administering a breath test to ensure the subject does not burp, vomit, or place anything in their mouth. Even a small deviation can affect the reading.
Partition Ratio And Scientific Uncertainty
Breath machines assume a standard partition ratio between breath alcohol and blood alcohol. That ratio varies among individuals. We often cross-examine the State’s witnesses about this scientific assumption and how it can produce inaccurate results.
Blood Test Challenges Under Texas Law
Blood tests are often viewed as stronger evidence, but they are also vulnerable to legal attack.
Warrant Issues
Under Supreme Court precedent, police generally need a warrant to draw blood unless valid consent is given. If the warrant affidavit lacks probable cause or contains false statements, we can move to suppress the blood result.
Chain Of Custody Problems
The State must prove that the blood sample tested is the same one drawn from the accused. Breaks in the chain of custody, labeling errors, or improper storage conditions can raise doubt about reliability.
Improper Storage And Fermentation
Blood must be preserved with appropriate chemicals and stored correctly. If not refrigerated or properly sealed, fermentation can artificially raise alcohol concentration levels.
Laboratory Errors
We review lab procedures, analyst qualifications, and quality control records. Human error happens in forensic labs. Cross-examination often reveals assumptions and procedural shortcuts.
Confrontation Clause Challenges
Under the Sixth Amendment, a defendant has the right to confront witnesses. If the State attempts to introduce lab reports without producing the actual analyst who performed the testing, we object. Courts have ruled that defendants have the right to question forensic analysts directly.
Administrative License Suspension Hearings
Under Texas Transportation Code § 524.011, a driver may face an administrative suspension in addition to the criminal case. These hearings provide an early opportunity to challenge:
- The legality of the stop
- Probable cause
- The validity of the refusal or test
Testimony obtained during these hearings can be used later in criminal court.
Scientific Defenses To Breath And Blood Testing
Alcohol absorption and elimination rates vary significantly. A person’s blood alcohol concentration can rise after driving but before testing. This is known as a “rising BAC” defense.
Medical conditions such as:
- GERD
- Diabetes
- Ketosis
can affect breath readings. Certain medications and mouth alcohol contamination also influence results.
We work with forensic toxicologists when necessary to present alternative explanations to the jury.
Suppression Motions And Pretrial Litigation
Before trial, we file motions to suppress illegally obtained evidence. If the judge grants suppression, the State may lose its strongest evidence. That often leads to dismissal or favorable plea negotiations.
Even when suppression is not granted, weaknesses in testing procedures can be used to create reasonable doubt before a jury.
Frequently Asked Questions About Breath And Blood Tests In Galveston DWI Cases
Can I Refuse A Breath Or Blood Test In Texas?
Texas has an implied consent law under the Transportation Code. If you refuse testing, your license can be suspended administratively. However, refusal does not automatically result in a criminal conviction. In some cases, refusal prevents the State from obtaining chemical evidence unless they secure a warrant. We evaluate whether refusal may have helped or harmed your defense based on the specific facts.
Do Police Always Need A Warrant For A Blood Draw?
Generally, yes. The Supreme Court has held that warrantless blood draws are usually unconstitutional unless voluntary consent is given. If officers claim consent but used pressure or misleading statements, we challenge whether consent was truly voluntary.
Are Breath Tests Always Accurate?
No machine is perfect. Breath testing devices rely on assumptions about human physiology. Environmental factors, maintenance issues, and user error can affect readings. We examine maintenance logs and testing protocols in every case.
What Happens If The Machine Was Not Properly Maintained?
Improper maintenance can undermine reliability. If calibration checks were missed or failed, the results may be excluded or given little weight by a jury.
Can Medical Conditions Affect Test Results?
Yes. Conditions such as acid reflux can introduce mouth alcohol into a breath sample. Diabetes and certain diets can produce compounds that interfere with breath testing devices.
How Long Does The State Have To Test My Blood?
Laboratories must follow established procedures. Delays, improper storage, or contamination can compromise results. We investigate storage logs and chain of custody documentation.
What If The Officer Did Not Observe Me Before The Breath Test?
Texas regulations require an observation period to prevent contamination. If that did not occur, the reliability of the breath test is questionable.
Can A Blood Test Be Wrong?
Yes. Blood testing involves human handling, chemical preservatives, and analytical equipment. Errors can occur at any stage. We analyze lab documentation for discrepancies.
Will A High Test Result Automatically Lead To Conviction?
No. The State must prove intoxication beyond a reasonable doubt. Even a high number can be challenged if the test was improperly obtained or scientifically unreliable.
Should I Hire A Lawyer Even If I Failed The Test?
Absolutely. Chemical test results are not self-proving. A thorough review of constitutional and scientific issues often reveals defenses that are not obvious at first glance.
Why Legal Representation Matters In Galveston DWI Cases
Breath and blood evidence often appear strong on paper. However, DWI cases are technical. They require knowledge of constitutional law, forensic science, and Texas criminal procedure. A careful review of every step, from the stop to the lab analysis, can expose weaknesses that make a difference in court.
A conviction under Texas Penal Code § 49.04 can result in fines, jail time, license suspension, and long-term consequences. Challenging chemical testing evidence is often central to protecting your record and your future.
Contact Mark Diaz & Associates For Your Free Consultation
If you have been charged with DWI in Galveston or anywhere in Houston, do not assume the breath or blood test result ends your case. At Mark Diaz & Associates, we examine every detail of the stop, arrest, warrant, and laboratory process. We fight to suppress unreliable evidence and protect your rights at every stage.
Contact our Galveston DWI lawyer at Mark Diaz & Associates today by calling 409-515-6170 to schedule your free consultation. The firm represents clients in Galveston and throughout the city of Houston, Texas.
When you hire me, you work directly with me. My clients have my personal cell phone number, because questions, emergencies, and concerns do not always happen during business hours. You will not be handed off to a junior associate or lost in a system where your case is one of dozens on a crowded docket. From arrest through resolution, I remain personally involved and accessible.
(409) 515-6170