Breath Test vs. Blood Test in Texas DWI Cases: What Helps or Hurts You?
Texas Breath Test vs. Blood Test: Which One Hurts or Helps Your DWI Defense?
In Montgomery County, BAC numbers aren’t the full story — evidence must be reliable.
The Breath Test
Texas uses the Intoxilyzer 9000 breath machine. The reading depends on computer algorithms — not a direct measurement of blood alcohol concentration.
Defense targets include:
- Calibration and maintenance logs
- Mouth alcohol contamination
- Medical conditions (GERD, diabetes)
- Operator certification issues
Key point: If any step was wrong, the “number” loses its credibility fast.
The Blood Test
Blood is typically taken at a hospital or using Montgomery County’s phlebotomy program — after the officer obtains a warrant if you refuse.
But blood evidence involves:
- Tube preservatives
- Storage/temperature issues
- Chain of custody proof
- Gas chromatography reliability
Any gap in documentation can justify suppression.
Common Defense Themes
- Was the stop legal? No lawful stop = no lawful arrest = everything suppressed.
- Was probable cause weak? Bodycam contradictions undermine validity.
- Did prosecutors meet scientific requirements? Texas Rule of Evidence 702 (expert reliability).
In Montgomery County, we regularly cross-examine lab analysts from the Houston Forensic Science Center about their process and possible contamination points.
Breath or Blood — The State Must Still Prove Intoxication
Texas Penal Code §49.01 allows prosecutors to claim intoxication based on:
- Loss of mental faculties
- Loss of physical faculties
- BAC at .08 or higher
So even a number below .08 does not guarantee dismissal — and a number above .08 isn’t a guaranteed conviction.
Which One Is “Better” for Defendants?
There is no universal answer — but:
- Breath tests are generally easier to challenge
- Blood tests often require deeper scientific attacks
We build your defense around the weakest link in the State’s process.
Protect Your Rights Immediately
If you gave a breath or blood sample — or refused — the next move is critical.
Call today: (936) 777-4891