Can Problems With a DPS Blood Analyst Affect a Texas DWI Case?

July 16, 2026

If you were arrested for DWI in Houston, Fort Bend County, Montgomery County, or anywhere in the greater Houston area, and the State is treating a blood-test number like the case is already over, take a breath. It is not over. A lab result is not the same thing as proof beyond a reasonable doubt, and how that number was produced matters just as much as what it says.

A blood draw can be challenged. The warrant can be challenged. The chain of custody can be challenged. The storage and refrigeration history can be challenged. The lab process can be challenged. And, in the right case, the credibility and reliability of the analyst behind the number can become one of the most important issues in the courtroom. That is exactly the kind of case-specific analysis an experienced Houston DWI lawyer should walk through with you before you decide how to proceed.

That is the practical lesson from State v. Momin, a 2026 decision from the Fourteenth Court of Appeals involving a Fort Bend County DWI conviction. The court affirmed a new trial after the defense learned that the DPS blood analyst connected to the case had been under investigation for quality problems and mishandling evidence in other criminal cases.

What happened in State v. Momin?

The facts matter because Momin was not a case where the blood number sat on top of overwhelming independent evidence. The officer did not stop the vehicle because of swerving, a crash, speeding, or dangerous driving. The stop began after the driver delayed briefly at a green light and because of an expired-registration issue.

After the stop, the officer reported signs he associated with intoxication, but the opinion also describes defense evidence that cut the other way. The driver had stopped properly at a red light, drove at the proper speed, did not almost hit another car or curb, and was able to follow instructions. The officer acknowledged that some commonly reliable DWI indicators were absent or disputed.

The blood evidence therefore became central. The defense challenged the blood draw and the handling of the sample. The nurse’s procedure was questioned, including hand-washing and disinfecting issues. The defense also pointed to conflicting dates on the toxicology request and chain-of-custody report, creating a possible three-day gap where the location and refrigeration status of the blood sample were not clearly established.

That context is why the undisclosed DPS analyst information mattered. The same analyst had quality incidents in other cases involving mixed-up blood kits and tubes, sealing problems, and other standard-operating-procedure concerns. Some incidents were ultimately assessed as major. If the defense had known that before trial, counsel could have cross-examined the analyst differently and tied those prior quality problems to the reliability questions already being raised in Momin’s case.

The trial judge who granted the new trial had also presided over the original trial. That mattered on appeal because the court of appeals reviewed the ruling with deference and asked whether a reasonable view of the record could support the trial judge’s decision. Given the contested intoxication evidence and the central role of the blood test, the court affirmed the new trial order.

Momin was a DWI case out of Fort Bend County. According to the opinion, the officer stopped the driver after he did not immediately move when a traffic light turned green and after the officer learned the vehicle registration had expired. The officer later reported signs he believed indicated intoxication, including alcohol odor and field-sobriety-test performance.

The driver refused to provide a breath or blood sample. Police obtained a search warrant, a nurse drew blood, and the State alleged that the blood analysis showed an alcohol concentration of 0.15 or more.

At trial, intoxication was heavily contested. The defense challenged the blood test, including alleged chain-of-custody problems, conflicting dates on the toxicology request and chain-of-custody report, blood-draw procedures, and reliability concerns. The jury convicted him, and the trial court sentenced him to 180 days in jail and a $500 fine, probated for 18 months.

After trial, the defense learned that the Montgomery County District Attorney’s Office had issued a Brady notice in an unrelated case involving the same DPS blood analyst. That notice disclosed several quality incidents under DPS review, including problems involving mixed-up blood kits and blood tubes, failure to seal a batch of cases properly, and other lab-quality issues. The defense filed a motion for new trial. The trial court granted it. The State appealed. The court of appeals affirmed.

The short answer: lab problems can matter, especially when the blood evidence is central.

The court did not hand every DWI defendant a win. A lab problem alone will not undo a conviction. But when the blood evidence carries the case and the State sits on information about the analyst’s own quality failures, that is exactly the kind of gap a defense lawyer has to press.

The decision is more fact-specific—and more useful—than that. The court focused on whether the undisclosed evidence about the analyst’s quality incidents was favorable and material under Brady v. Maryland. Because intoxication was heavily contested and the defense had already attacked the blood evidence, information showing a pattern of analyst mistakes could have given the defense stronger impeachment and reliability arguments.

For DWI defendants, the point is simple: when the State’s case depends on scientific evidence, the defense has to investigate the science, the paperwork, the people, and the disclosures behind it.

What is Brady evidence?

Brady v. Maryland is the U.S. Supreme Court case that requires the government to disclose favorable, material evidence to the defense. Favorable evidence includes both evidence that tends to help prove innocence and impeachment evidence that can be used to challenge a State witness.

In a DWI blood case, Brady-type evidence might include information that calls into question the reliability of the blood test, the credibility of the analyst, problems with the lab, chain-of-custody issues, or facts that would help the defense cross-examine a State witness.

In Momin, the State argued that the undisclosed evidence was not favorable or material. The court disagreed. The analyst’s prior quality incidents could have been used to challenge his competence, his work product, and the reliability of the blood-test result.

Why the court treated the analyst issues as important

The court emphasized several facts that made the undisclosed evidence matter.

First, the defense had already challenged the blood evidence at trial. This was not a case where the blood result was a minor detail. The State alleged a result of 0.15 or more, and the defense disputed the reliability of the draw, storage, chain of custody, and testing process.

Second, the analyst’s other quality incidents were not merely character attacks. The defense was not trying to say, in a generic way, that the analyst was a bad person or generally untruthful. The issue was whether his mistakes and violations of lab procedures could undermine confidence in his work and the blood-test evidence.

Third, the court distinguished this case from other cases where the evidence of intoxication was overwhelming or where the lab mistake was isolated. In Momin, the court described the non-blood evidence as far from overwhelming and noted that intoxication was hotly contested.

Why this matters in Houston, Fort Bend, and Montgomery County DWI cases

Blood-test DWI cases are common in the Houston area. Police may seek a warrant after a refusal. A nurse or technician may draw blood. The sample may be transported, stored, refrigerated, logged, submitted, tested, reviewed, and reported before it ever appears in court.

Every step creates potential issues. The State may present the final number as clean science. A defense lawyer should ask how that number was produced, who handled the sample, what records exist, whether the sample was stored correctly, whether the analyst followed procedure, and whether the State disclosed information that could be used to challenge the result.

This is especially important in Fort Bend County, Harris County, and Montgomery County because DWI cases often move quickly, and early decisions can affect license consequences, bond conditions, plea negotiations, and trial strategy.

DWI blood evidence checklist

Issue to review	Why it matters
The stop	If the stop was unlawful, later evidence may be subject to suppression.
The warrant or consent issue	A forced blood draw generally requires careful review of the warrant, affidavit, timing, and scope.
Blood-draw procedure	Improper draw procedures can create reliability and contamination arguments.
Chain of custody	Gaps, conflicting dates, or unexplained handling can undermine confidence in the result.
Storage and refrigeration	Blood storage conditions can matter, especially when records conflict or are incomplete.
Lab and analyst records	Quality incidents, SOP violations, and analyst issues can affect cross-examination and reliability.
Disclosure history	The defense should examine whether Brady, Giglio, and Texas discovery obligations were satisfied.

What prosecutors may argue

In a DWI blood case, prosecutors may argue that the blood-test number is objective, scientific, and more reliable than field sobriety testing or officer observations. They may also argue that any lab issue from another case has nothing to do with the defendant’s sample.

Sometimes that argument may work. But Momin shows why it should not be accepted without scrutiny. If an analyst has quality incidents involving blood kits, tubes, sealing, labeling, chain-of-custody awareness, or lab procedure, the defense may have a legitimate basis to argue that the jury should know about those problems—especially when the defense is already challenging the reliability of the blood evidence.

What the defense should examine

A strong DWI defense does not stop with the breath or blood number. It should include a detailed review of the stop, field investigation, warrant, blood draw, storage, chain of custody, lab testing, analyst records, and disclosure history.

For blood cases, the defense should look for conflicts between forms, missing refrigeration records, unexplained gaps in the evidence trail, blood-draw protocol problems, expired tubes, improper preservatives or anticoagulants, analyst notes, technical-review records, lab-quality incidents, and any notices that should have been disclosed.

The defense should also compare the scientific evidence against the officer’s observations. If the officer did not see bad driving, if the client followed instructions, if field tests were questionable, or if other signs of intoxication were weak, the reliability of the blood test may become even more important.

Common mistakes defendants make after a DWI blood test

The first mistake is assuming the case is over because the State has a blood number. A blood result is evidence, not a conviction.

The second mistake is waiting too long. DWI cases have time-sensitive issues, including ALR deadlines, video preservation, witness availability, and discovery demands.

The third mistake is focusing only on the number and ignoring the process. In many DWI cases, how the evidence was collected and handled matters as much as the reported result.

How The Napier Law Firm approaches DWI blood-test cases

The Napier Law Firm reviews DWI blood cases from multiple angles. We look at whether the stop was lawful, whether the warrant was valid, whether the blood draw complied with procedure, whether the chain of custody is complete, whether the lab records support the reported number, and whether the State disclosed the information the defense was entitled to receive.

George Napier’s background as a former prosecutor is useful here. The defense is not just asking whether something looks wrong after the fact. It is asking how the State is likely to prove the case, where the prosecutor may expect little resistance, and what issues can change the negotiation or trial posture.

Related Napier Law resources

Source links for website company

State v. Momin opinion: Read opinion
Brady v. Maryland, 373 U.S. 83 (1963)
Texas Code of Criminal Procedure art. 39.14
Texas Rule of Evidence 608(b), if impeachment scope is discussed

Charged With DWI in Texas? The Napier Law Firm Can Help.

If you are facing a DWI charge in Houston, Conroe, Harris County, Montgomery County, or Fort Bend County, do not assume the State’s blood-test result tells the whole story. The Napier Law Firm can review the stop, the warrant, the blood draw, the lab records, and the State’s disclosure obligations before you decide how to fight the case.

Call (713) 470-4097 or request a free consultation.