A traffic stop on Preston Road or near the Dallas North Tollway can turn serious fast. In Texas, drivers suspected of being intoxicated face strict laws, and a blood or breath test often becomes the centerpiece of a DWI case. But alcohol does not absorb into the body all at once. Because of this, one of the most strategic defenses in a Texas DWI case is known as the “rising BAC” defense.
This defense challenges whether the test results actually reflect your level of intoxication at the time you were driving. In Collin and Denton County courts, where Frisco cases are often heard, this can mean the difference between a conviction and a dismissal.
What Are Texas’s DWI Laws?
Texas Penal Code §49.04 makes it a crime to operate a motor vehicle in a public place while intoxicated. “Intoxicated” means either not having the normal use of mental or physical faculties because of alcohol or drugs, or having a blood alcohol concentration (BAC) of 0.08 or higher.
For many drivers, the arrest hinges on whether that number—0.08—was accurate at the time they were actually behind the wheel. The law does not say “0.08 at the police station.” It applies to the moment of driving. That distinction is where the rising BAC defense comes in.
How Does Alcohol Absorption Work?
When someone drinks, alcohol takes time to move from the stomach and small intestine into the bloodstream. Factors such as:
- Body weight and gender
- Food consumption before or during drinking
- Type of alcohol and speed of consumption
- Metabolism and health conditions
All influence how quickly BAC rises.
In many cases, a person’s BAC is still climbing for 30 minutes to two hours after their last drink. That means a driver could be under the legal limit when pulled over, but test above the limit an hour later at the station.
The Science Behind the Rising BAC Defense
The rising BAC defense argues that test results do not match the driver’s actual BAC while operating the vehicle. Instead, the BAC was lower at the time of driving and only crossed the 0.08 threshold later, due to ongoing absorption.
For example, if an officer stops a driver at 11:00 p.m. and conducts a breath test at 11:45 p.m., the result may show 0.09. But if the driver had just finished a drink before leaving a restaurant, their BAC might have been closer to 0.06 while driving.
This defense can be supported by toxicologists, scientific studies, and cross-examination of how and when the test was administered.
Why Is Timing So Important in Texas DWI Cases?
Texas law allows officers to request breath or blood tests, and refusal can trigger license suspensions under the state’s implied consent laws. But tests are rarely immediate. Transport, waiting periods, and paperwork mean there is often a significant gap between the stop and the test.
That delay can be crucial. A prosecutor may present a number like 0.10 or 0.12, but the defense can show that the actual BAC at the time of driving was below 0.08. This creates reasonable doubt about whether the legal standard for intoxication was met.
How Do Prosecutors Respond?
Prosecutors often counter rising BAC arguments by:
- Using retrograde extrapolation, a method of estimating BAC at the earlier time of driving
- Arguing that field sobriety tests showed impairment regardless of the BAC number
- Pointing to officer observations like slurred speech, odor of alcohol, or erratic driving
Retrograde extrapolation, though, depends on assumptions about drinking patterns and body chemistry. If those assumptions are flawed or unsupported, the defense can challenge their credibility.
DWI Cases in Frisco
Frisco drivers arrested for DWI typically see cases filed in Collin County or Denton County courts, depending on the arrest location. Judges and juries in these courts are used to hearing technical testimony about alcohol testing. That makes preparation and knowledge of both science and procedure critical.
Major traffic routes like Main Street, Lebanon Road, or State Highway 121 are frequent locations for DWI stops. Officers often rely heavily on breath tests conducted later at the jail, making the timing issue central for many local cases.
Other Defenses That May Work Alongside Rising BAC
A strong defense rarely rests on one argument alone. The rising BAC defense may be combined with:
- Challenging the legality of the traffic stop
- Questioning field sobriety test reliability
- Highlighting improper calibration or maintenance of breath test machines
- Scrutinizing the chain of custody for blood samples
Each piece adds to reasonable doubt, and Texas law requires prosecutors to prove intoxication beyond a reasonable doubt.
Can Our Firm Help You Beat Your DWI?
Science-based defenses like rising BAC require attorneys who know both the law and the technical aspects of alcohol testing. Cross-examining state experts, presenting alternative scientific evidence, and making jurors understand timing gaps takes experience and preparation.
At the Law Offices of Biederman & Burleson P.L.L.C., we have built a record of dismissals and not guilty verdicts across North Texas. Our team combines aggressive courtroom skills with a clear understanding of how science can work in your favor.
Take Action If You Face a DWI in Frisco
A DWI charge in Texas can threaten your license, job, and freedom. If your arrest involved a breath or blood test taken well after you stopped driving, the rising BAC defense could be an important part of your case.
We are ready to analyze the evidence, expose weaknesses in the prosecution’s timeline, and fight for your future. Call us today at 469-517-3364 to schedule a consultation.
