Why "Over the Legal Limit" Doesn't Mean Guilty
A BAC reading above .08 is not proof of guilt under Texas law. Texas Penal Code §49.04 requires the state to prove intoxication at the time of driving — not at the time of testing. Chemical tests are typically administered 30 to 90 minutes after a traffic stop. The result reflects BAC at the station, not necessarily what existed while the vehicle was moving. This distinction is the foundation of BAC-based defenses.
Herman Martinez holds NHTSA certification in breathalyzer protocols and standardized field sobriety testing. That is the same training Texas peace officers must complete. He understands Intoxilyzer 9000 tolerances, operator requirements, chain-of-custody standards, and laboratory analytical protocols. He does not learn about these tests from legal briefs. He uses insider technical knowledge to identify precisely where each test failed — and why that failure matters in front of a judge and jury. A breath and blood test lawyer Houston with this technical background identifies test failures other attorneys simply miss.
How Can a Breath Test Result Be Challenged in a Texas DWI Case?
Texas designates the Intoxilyzer 9000 as its sole approved evidential breath testing instrument. The machine uses infrared spectroscopy to estimate blood alcohol concentration from deep lung air. It requires calibration every 90 days, a certified operator, and a 15-minute uninterrupted observation period before testing begins. Each of these requirements is an independent challenge point when records show deviation. A breath and blood test lawyer Houston checks every one of these requirements before accepting a breath result at face value.
The Intoxilyzer 9000 must be calibrated on a schedule set by the Texas Department of Public Safety. Herman subpoenas the machine's complete service history. Missing calibration dates, out-of-tolerance reference solution results, or unresolved maintenance flags are documented grounds for challenging the accuracy of the reading produced.
Residual mouth alcohol elevates breath test readings without reflecting true blood alcohol. GERD, recent burping, dental work, and mouthwash all introduce mouth alcohol. Texas DPS protocol requires a continuous 15-minute observation period before testing to allow mouth alcohol to dissipate. Officers who fail to complete this observation period produce an invalid result.
The Intoxilyzer 9000 calculates BAC by applying a fixed 2,100:1 breath-to-blood partition ratio. This ratio is a population average. Individual ratios range from 1,700:1 to 2,400:1. If your actual ratio is 1,700:1, the machine overstates your BAC by approximately 23 percent. Partition ratio variance is a recognized scientific challenge in Texas courts.
Body temperature directly affects breath test accuracy. A fever of 1°C raises breath test readings by approximately 7 percent. Diabetics in ketosis produce isopropyl alcohol as a metabolic byproduct that some Intoxilyzer units cannot distinguish from ethanol. GERD, asthma, and high-protein ketogenic diets also generate interferents that mimic alcohol on infrared spectroscopic analysis.
Texas DPS requires breath test operators to hold a current, active operator certification at the time of each test administered. An expired certification renders the result inadmissible. Herman requests the operator's full certification history through discovery in every breath test case. Lapsed certifications appear more frequently than prosecutors anticipate. A breath and blood test lawyer Houston requests full operator history in every single breath test case.
How Can a Blood Test Be Challenged in a Texas DWI Case?
A blood test directly measures alcohol concentration in a collected sample. Courts treat blood tests as more accurate than breath tests. However, accuracy requires proper draw technique, correct preservative chemicals in the collection tube, documented refrigeration, certified laboratory analysis, and an unbroken chain of custody. A documented defect in any of these steps is grounds for suppression of the result. A breath and blood test lawyer Houston reviews every one of these steps for the documented defect that can suppress the result.
Chain of custody documents every person who handled the blood sample from draw to laboratory result. Texas courts require this chain to be unbroken and fully documented. A missing signature, unlogged transfer, or unlabeled vial creates reasonable doubt that the sample tested was the sample drawn from the defendant.
Texas DPS crime laboratories must maintain accreditation under Texas Forensic Science Commission standards. Herman subpoenas analyst certifications, instrument validation logs, and method-specific quality control records. Using an unapproved testing method or an unaccredited analyst on the specific sample is grounds to challenge the reported BAC result.
Blood samples ferment when improperly preserved, generating ethanol inside the collection tube independent of actual alcohol consumption. Each gray-top collection tube must contain sodium fluoride as a preservative and potassium oxalate as an anticoagulant. Herman examines refrigeration logs and preservation records. Fermentation in an improperly stored sample can produce a falsely elevated BAC reading.
Under Missouri v. McNeely (2013), police must obtain a search warrant before a non-consensual blood draw in most DWI cases. Natural alcohol dissipation alone does not constitute exigent circumstances. A warrantless draw lacking a recognized exception to the warrant requirement violates the Fourth Amendment. Herman moves to suppress all warrantless blood draws where no valid exception applies. A breath and blood test lawyer Houston moves to suppress every warrantless blood draw lacking a valid exception.
What Is the Rising Blood Alcohol Defense in Texas?
The rising BAC defense is a recognized legal and scientific argument in Texas DWI cases. Alcohol absorption continues for 30 to 90 minutes after the last drink. A driver stopped shortly after drinking may have a sub-.08 BAC while operating the vehicle, with the BAC continuing to rise through the stop and test period. This gap between driving BAC and testing BAC is the foundation of the defense.
Herman retains forensic toxicologists to perform retrograde extrapolation analysis. The analysis works backward from the documented test result to estimate BAC at the time of the traffic stop. The defense is most effective when a significant delay exists between the stop and the test. A 45-minute gap between the traffic stop and breath test, for example, provides substantial extrapolation range that supports a sub-.08 driving BAC argument. A breath and blood test lawyer Houston retains forensic toxicologists specifically to support this rising-BAC argument with real science.
Most defense attorneys challenge breath and blood tests by reading about them in legal briefs. Herman Martinez has completed the same NHTSA breath test operator certification course that Texas peace officers must complete. He understands machine tolerances, reference solution acceptance ranges, and operator error categories at the technical level. That distinction changes how cross-examination of the breath test operator unfolds before a judge and jury.
Chemical test challenges work best when combined with a review of the traffic stop itself. An unlawful stop suppresses all downstream evidence, including breath and blood test results. See Herman's analysis of challenging unlawful traffic stops. Field sobriety tests typically precede the chemical test and carry their own independent challenge grounds — read about field sobriety test challenges. Texas imposes a strict 15-day deadline to contest your license suspension after arrest — that deadline is already running. Learn more about ALR hearings in Texas. A breath and blood test lawyer Houston reviews the traffic stop, the field sobriety tests, and the chemical test together as one connected challenge.
Common Questions About Breath & Blood Tests
Refusing the breath test removes the state's most direct BAC evidence but triggers an automatic ALR license suspension. Under Texas Transportation Code §724.035, refusal results in a 180-day suspension for a first offense — twice the 90-day penalty for a failed test. Herman defends both refused and submitted test cases with equal effectiveness. Contact him immediately regardless of which choice you made at the scene.
Yes. The state must prove intoxication at the time of driving, not at the time of testing. A BAC above .08 at the station does not automatically establish the same BAC existed while the vehicle was moving. Herman has won jury trials where breath test results exceeded .08 by challenging machine calibration records, the 15-minute observation period, and the rising BAC defense supported by forensic toxicology testimony. A breath and blood test lawyer Houston has won jury trials on exactly this argument more than once.
Yes. Under Texas Transportation Code §724.019, a person who submits to a chemical test has the right to request an independent blood sample drawn at their own expense. This counter-sample either corroborates a lower BAC or provides independent data to compare against the state's result. Herman coordinates independent testing requests as a standard component of early case investigation.
A breath test estimates blood alcohol indirectly from deep lung air using infrared spectroscopic analysis. A blood test directly measures alcohol in a collected sample. Blood tests carry greater inherent accuracy but introduce chain of custody, preservation, and contamination vulnerabilities that breath tests do not. Herman challenges each type through different but equally effective legal and scientific strategies.
Yes, in specific circumstances defined by Texas Transportation Code §724.012. Mandatory blood draws without consent apply when a crash involved death or serious bodily injury, when the DWI involved a child passenger, or when the driver has two or more prior DWI convictions. Mandatory draws still require proper collection technique and chain of custody. Herman challenges collection procedure and documentation in all mandatory draw cases. A breath and blood test lawyer Houston challenges collection procedure and documentation in every mandatory draw case.
The Intoxilyzer 9000 is accurate only when calibrated, properly operated, and used within its published specifications. Texas DPS requires calibration every 90 days, a certified operator, and a completed 15-minute observation period before each test. Deviations from any of these requirements create a documented basis for challenge. Herman subpoenas maintenance logs, calibration records, and operator certification history in every breath test case. A breath and blood test lawyer Houston subpoenas the complete maintenance and calibration file in every case.
The rising BAC defense argues that a defendant's BAC was below .08 at the time of driving, even if it exceeded .08 during later testing. Alcohol absorption continues for 30 to 90 minutes after the last drink. The defense is most effective when a significant delay existed between the traffic stop and the chemical test. Herman supports this argument with forensic toxicology retrograde extrapolation testimony from qualified experts.
Yes. GERD causes stomach gases containing alcohol to enter the mouth, artificially elevating breath test readings above true blood alcohol. Diabetes in ketosis generates isopropyl alcohol as a metabolic byproduct that some Intoxilyzer units misidentify as ethanol. High-protein and ketogenic diets also produce acetone. Herman investigates medical history and prescription records as part of every breath test challenge.
Blood test chain of custody is challenged by documenting every gap between collection and laboratory analysis. An unlabeled vial, missing transfer log entry, period of unrefrigerated storage, or uncertified collection technician each creates reasonable doubt about sample integrity. Herman obtains complete chain of custody documentation through discovery and subpoenas every individual who handled the sample from draw through reporting.
Yes. Breath test machine records are discoverable in Texas DWI cases. Herman subpoenas the Intoxilyzer 9000's maintenance logs, calibration results, reference solution records, and the administering operator's full certification history. These records regularly reveal out-of-tolerance calibrations, deferred maintenance entries, or lapsed certifications that provide grounds to exclude the test result from evidence entirely.