Texas DPS Intoxilyzer 9000 results carry a manufacturer margin of error of roughly ±0.005 to ±0.01 g/210L, so a 0.085 reading can fall below the 0.08 limit the State must prove under Tex. Penal Code § 49.04. L and L Law Group challenges calibration, observation, and operator error.
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Texas Bar verified. Reggie London (Texas Bar No. 24043514) and Njeri London (Texas Bar No. 24043266) are the co-founding partners of L and L Law Group, PLLC — based at 5899 Preston Rd, Suite 101 in Frisco, Texas (Collin County), with many 5-star Google reviews, and available 24/7 for criminal defense consultations.
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📖 2 min read362 wordsLast reviewed: 2026-05-13
Texas DWI cases live or die on breath test results. The Intoxilyzer 9000 used in Texas has a published margin of error of roughly ±0.005 to ±0.01 g/210L, with additional uncertainty from calibration, environmental factors, and operator error.
The published Intoxilyzer 9000 margin of error
CMI, Inc., the manufacturer of the Intoxilyzer 9000 used by Texas DPS, publishes a manufacturer-tolerance margin of error of ±0.005 g/210L at low BACs and ±0.01 g/210L at higher BACs. The Texas Breath Alcohol Testing Program adds its own protocol requirements: two breath samples within 0.02 of each other, calibration checks before and after, and biennial inspection of the instrument.
Beyond the published margin: real-world variability
The published margin assumes proper calibration, proper sample collection (deep lung air), and proper operator administration. Real-world cases routinely show variability beyond ±0.01 due to: temperature variation in the testing environment; radio-frequency interference from nearby equipment; mouth alcohol from belching, GERD, or recent food/drink within the 15-minute observation period; operator failure to observe the suspect for the full 15 minutes; instrument drift between calibration checks.
The 0.08 question and the 0.005 buffer
For a 0.085 reading, the margin of error analysis matters enormously. The State must prove BAC of 0.08 or above beyond a reasonable doubt. If the published instrument margin is ±0.005, the true value could be anywhere from 0.080 to 0.090. That alone doesn't require acquittal, but it shifts the burden of proof analysis. Add real-world variability and the case for reasonable doubt grows.
How we challenge breath tests
(1) We subpoena the instrument's calibration and maintenance records. (2) We retain a breath-test expert to review the certification, the printouts, and the operator's qualifications. (3) We cross-examine the operator on the 15-minute observation period and the deep-lung-air sampling. (4) We file motions in limine to exclude testimony beyond the scope of the operator's personal knowledge.
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In our practice defending Texas criminal cases, we have represented clients in Collin, Dallas, Denton, and Tarrant County criminal courts on the full Texas Penal Code and Health & Safety Code spectrum. Reggie's prosecutor background in Dallas County means we know the State's evidentiary playbook; Njeri's trial-trained motion practice anchors the suppression-driven defense work.
Last reviewed: 2026-05-13 by Njeri London and Reggie London, co-founding partners, L and L Law Group, PLLC. This content is reviewed for accuracy at least every 12 months and when statutory or case-law changes occur.
Attorney Advertising Disclosure. This content is for general informational purposes only and is not legal advice. Reading this content or contacting L and L Law Group, PLLC through this website does not create an attorney-client relationship. Prior results do not guarantee a similar outcome. Past performance is not a guarantee of future results.
About the Authors
Njeri London
Co-Founding Partner
Texas Bar No. 24043266. Admitted: TXND, TXED, 5th Circuit. Thurgood Marshall School of Law. Focus: Fourth Amendment motion practice, drug-crime defense, federal cases. Verify on Texas Bar
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L&L Law Group represents clients across North Texas counties for DWI, assault, drug crimes, juvenile defense, outstanding warrants, bond reduction, and expunction matters.
