Why the Process is as Important as the Result
Texas DWI Defense Attorney
In many Texas DWI cases, a Blood Alcohol Concentration (BAC) number above 0.08% feels like an automatic conviction. However, at Beltz Law Group, we know that a BAC result is only as reliable as the journey the blood took from your arm to the laboratory.
If the State cannot account for every second that your blood sample was in transit or storage, or if the lab failed to follow strict scientific protocols, the evidence may be ruled inadmissible. This is known as the Chain of Custody defense.
What is the Chain of Custody?
The Chain of Custody is a documented, unbroken chronological record of everyone who had physical possession of your blood sample. Under Texas Code of Criminal Procedure Article 38.42, the State must provide an affidavit or testimony detailing:
- Who drew the blood.
- Who transported it to the evidence locker.
- Who moved it from the locker to the lab.
- Who broke the seal to perform the analysis.
If there is a “gap” in this chain—such as an unrecorded transfer or a missing signature—the reliability of the sample is compromised. A gap allows for the possibility of tampering, contamination, or a simple mix-up with another person’s blood.
Common Laboratory Errors
DWI Attorney North Texas
Even if the chain of custody is intact, the science inside the lab is often vulnerable. We investigate several common failure points:
1. Fermentation (The “Living” Sample)
Blood is organic matter. If it is not properly refrigerated or if the vial does not contain the correct amount of sodium fluoride (a preservative), it can ferment. Fermentation produces “new” alcohol inside the vial. In some cases, a person who was legally sober at the time of the draw could “test” as intoxicated weeks later because the sample created its own alcohol while sitting in a warm evidence room.
2. Carryover Contamination
Labs use a machine called a Gas Chromatograph to test blood. If the technician does not properly clean the machine or run “blank” samples between tests, alcohol from a high-BAC sample can “carry over” into the next test, falsely inflating the result for the next person.
3. Improper Site Sterilization
Before drawing blood, the technician must clean the skin. If they use a standard alcohol swab, they may accidentally introduce alcohol into the needle and the sample. Forensic protocols require the use of non-alcoholic cleaners like povidone-iodine.
The Power of the Motion to Suppress
North Texas DWI Attorney
If we find evidence of lab errors or a broken chain of custody, we file a Motion to Suppress. If the judge agrees that the evidence is unreliable, the BAC result is thrown out entirely. Without that “magic number,” the prosecutor is left with only the officer’s subjective observations, which are much easier to challenge in front of a jury.
Why Strategy Matters
Challenging a lab result requires more than just pointing out a mistake; it often requires hiring independent forensic experts to review the lab’s “litigation packet”—the hundreds of pages of raw data, calibration logs, and chromatograms that the State rarely shows the defendant. At Beltz Law Group, we know how to read between the lines of those reports to find the truth.
Is your BAC result surprisingly high? It might not be your body that’s the problem—it might be the lab’s process. Let us help you investigate the “science” behind your charges.
