Texas DWI Blood Warrants: 10 Defense Issues to Check

Police got a warrant. They drew your blood. The laboratory reported a BAC over the legal limit.

That does not mean the DWI case is over.

When I review a Texas DWI blood warrant case, I do not simply look at the number printed on the laboratory report. I want to know how police obtained the warrant, what they told the magistrate, how the blood was collected, what happened to the sample afterward, how the laboratory analyzed it, and what the final result actually proves about the person’s condition at the time of driving.

Texas defines intoxication in part as having an alcohol concentration of 0.08 or more, but the DWI allegation concerns whether the person was intoxicated while operating the vehicle—not simply whether a later blood sample produced a particular number.

Here are 10 issues I examine when defending a Texas DWI blood-warrant case.

A Blood Warrant Does Not Automatically Prove DWI

A Texas DWI blood warrant generally allows police to obtain a blood specimen after presenting facts to a magistrate that establish probable cause. Texas law specifically provides for warrants used to collect blood specimens in intoxication investigations.

But there is an important distinction:

A warrant authorizing police to obtain blood is not the same thing as proof beyond a reasonable doubt that someone committed DWI.

The warrant, the blood draw, the handling of the specimen, the laboratory analysis, and the State’s interpretation of the result can present separate issues.

That is why my investigation does not end when I see the words “search warrant.”

It starts there.

1. Did Police Have Probable Cause?

The first thing I want to know is why the officer believed there was probable cause for DWI.

What happened before the arrest?

I look at the alleged driving behavior, the reason for the traffic stop, body-camera and dash-camera footage, witness statements, statements attributed to the driver, field sobriety testing, alleged odors, physical observations, and anything else police relied upon.

Then I compare the evidence with what appears in the warrant affidavit.

Texas courts generally give deference to a magistrate’s probable-cause determination. That does not make the affidavit immune from scrutiny. The question remains whether the facts actually presented to the magistrate supplied a substantial basis for finding probable cause.

A lawyer reviewing a DWI blood warrant in Texas should therefore investigate the entire sequence leading to the warrant—not just the laboratory report produced afterward.

2. What Did the Officer Tell the Magistrate?

I want the warrant affidavit.

Then I read it carefully.

A blood-warrant affidavit may describe observations such as driving behavior, an odor of alcohol, admissions about drinking, field sobriety testing, a refusal to provide a voluntary specimen, or other facts the officer believes establish probable cause.

But an affidavit should not be evaluated in isolation from the evidence.

If an officer says the driver exhibited certain clues on field sobriety tests, I want to watch the video.

If the affidavit describes erratic driving, I want to see whether that driving was captured on camera.

If the officer attributes a statement to the driver, I want to hear the actual statement when a recording exists.

Small differences can matter.

Sometimes what appears straightforward on paper looks considerably different when compared with the video and other evidence.

3. Did the Affidavit Omit or Misrepresent Important Facts?

The next question is not merely what the affidavit says.

It is also what it doesn’t say.

Courts recognize procedures for challenging material false statements in warrant affidavits, and Texas appellate courts have also addressed material omissions under that framework. The precise legal requirements are important: not every mistake, disagreement, or omitted fact invalidates a warrant.

That is why I compare the affidavit line by line against the available evidence.

Was an important fact described inaccurately?

Was potentially significant information omitted?

Does the video contradict something presented to the magistrate?

Would correcting the challenged information affect the probable-cause analysis?

Those questions can become important when deciding whether there is a legitimate basis to challenge a blood draw warrant in Texas.

4. Was the Warrant Properly Issued and Executed?

Even when probable cause exists, I examine the warrant itself and how officers executed it.

Among other things, I want to know:

• Who issued the warrant?
• When was it issued?
• What exactly did it authorize?
• When was the blood taken?
• Who executed the warrant?
• Did what actually happen fall within the warrant’s authorization?

Texas law contains specific provisions governing search warrants and warrants for blood specimens in intoxication cases. For example, Article 18.067 of the Texas Code of Criminal Procedure addresses execution of certain intoxication-offense blood warrants, and Article 18.07 requires the issuing magistrate to endorse the date and hour of issuance on a search warrant.

I do not assume those requirements were followed simply because a warrant exists.

I check.

5. How Much Time Passed Between Driving and the Blood Draw?

Timing can become one of the most important issues in a blood case.

A blood sample tells us the alcohol concentration in the specimen collected at a particular time.

The DWI case concerns the defendant’s condition while operating the vehicle.

Those are not necessarily the same moment.

I build a timeline:

Time of alleged driving → traffic stop or accident → investigation → arrest → warrant application → warrant issuance → transportation → blood draw.

Then I examine the gap.

Texas courts have recognized that a later alcohol test can be relevant evidence without necessarily establishing the person’s exact BAC at the earlier time of driving. Other evidence surrounding the driving and alleged intoxication remains important.

The longer and more complicated that timeline becomes, the more carefully I want to examine what conclusions the State intends to draw from the laboratory number.

6. Who Drew the Blood and How Was It Collected?

Blood evidence does not magically appear in a laboratory vial.

A person has to collect it.

Texas Transportation Code § 724.017 identifies who may take a blood specimen at the request or order of a peace officer under Chapter 724. The statute includes physicians, qualified technicians, registered professional nurses, licensed vocational nurses, and certain authorized emergency medical personnel. It also provides that the specimen must be taken in a sanitary place.

So I want to know:

Who performed the draw?

What were that person’s qualifications?

Where was the blood collected?

What collection kit was used?

Were the appropriate tubes used?

How were they labeled?

Were the collection procedures documented?

Were there irregularities in the paperwork or procedure?

A DWI blood test lawyer should understand that the laboratory analysis is only one part of the process. The integrity of the evidence begins at collection.

7. Was the Blood Properly Preserved and Stored?

After the blood enters the tube, another part of the investigation begins.

What happened to it?

Blood specimens used in DWI investigations must travel from the collection site to wherever they are stored and eventually to the laboratory.

I want records showing how that occurred.

Depending on the circumstances, questions can include whether the sample was properly sealed and labeled, how and where it was stored, how long it remained there, and whether there is documentation accounting for its handling.

This is where the defense investigation moves beyond the police report.

The State wants the jury to trust a number.

Before deciding how much confidence that number deserves, I want to understand the history of the sample that produced it.

8. Can the State Establish Chain of Custody?

Chain of custody asks a fundamental question:

Can the State adequately account for the evidence from collection through testing?

Who possessed the blood?

When was it transferred?

Where was it stored?

Who received it at the laboratory?

Are the identifying numbers consistent across the blood kit, submission paperwork, evidence records, and laboratory documentation?

Does the documentation contain unexplained discrepancies?

Not every paperwork problem means blood evidence will automatically be excluded. But chain-of-custody records can reveal issues that deserve investigation.

The firm’s existing legal library also includes prior coverage specifically addressing the State’s establishment of chain of custody, making that a useful internal resource for readers who want to understand this evidentiary issue in greater detail.

9. Was the Laboratory Testing Reliable?

Once I get to the laboratory evidence, I do not stop at the final report.

I want to understand how the number was produced.

Blood alcohol testing commonly involves gas chromatography, and evaluating the laboratory portion of a case may require examining much more than a single certificate showing the reported BAC.

Depending on the case, that can mean reviewing underlying analytical data, quality-control information, calibration-related records, laboratory procedures, documentation associated with the testing sequence, and other information relevant to whether the analysis was performed reliably.

The firm’s existing DWI resources include a detailed discussion of gas chromatography and how it is used to determine blood alcohol concentration.

The larger point is simple:

“The lab says .___” should not be the end of the investigation.

It should trigger another set of questions.

10. What Does the Result Actually Prove About BAC at the Time of Driving?

This may be the most important question in the entire blood case.

Suppose someone’s blood was drawn well after the traffic stop and the laboratory reported a BAC above 0.08.

What was that person’s alcohol concentration when they were actually driving?

Alcohol is absorbed and eliminated over time. Determining a person’s BAC at an earlier point may raise issues involving the timing of alcohol consumption, absorption, elimination, the timing of the blood draw, and the assumptions used in any retrograde-extrapolation analysis.

Texas courts have addressed this distinction. A later test result can be relevant evidence for a jury to consider, but the State still has to prove intoxication while the person was operating the vehicle.

That matters.

The number on the laboratory report is evidence.

It is not a substitute for analyzing the entire case.

Can a Texas DWI Blood Result Be Suppressed?

Potentially.

Whether suppression is available depends on the specific facts and law applicable to the case.

Texas appellate courts have ordered or upheld suppression in cases involving unconstitutional warrantless blood draws. For example, courts applying the Fourth Amendment have held that the State cannot rely solely on Texas’s mandatory-draw provisions to justify a nonconsensual, warrantless blood draw when no independent exception to the warrant requirement applies.

A case involving an actual warrant requires its own analysis.

Possible issues may involve probable cause, the contents of the affidavit, material misstatements or omissions, execution of the warrant, or other constitutional and evidentiary questions.

There is also an important caution: identifying a defect does not necessarily mean the evidence will be suppressed. Texas courts have applied a good-faith exception in some warrant cases.

That is why a motion to suppress should be based on the actual record rather than an assumption that every technical issue invalidates the blood evidence.

Can You Win a DWI Even With a High Blood Result?

A high reported BAC can be powerful evidence for the prosecution.

But it does not make the rest of the case irrelevant.

At Zendeh Del & Associates, PLLC, we have handled DWI cases in which significant alcohol-test results did not prevent favorable outcomes.

Our published case results include:

• A not-guilty verdict in a DWI jury trial involving a .20 blood result.
• A dismissed DWI case involving a warrant blood draw and reported BAC of .176.
• A dismissed DWI case involving a reported .306 BAC.

The firm’s published results page confirms the .20 not-guilty verdict and the .176 and .306 dismissals. Past results do not guarantee or predict the outcome of another case because every DWI prosecution involves different facts and evidence.

Those cases illustrate why I do not evaluate a DWI defense by looking at one number.

I investigate the stop.

I investigate the officer.

I investigate the warrant.

I investigate the blood draw.

I investigate the chain of custody.

I investigate the laboratory.

And finally, I ask what the State can actually prove about intoxication at the time of driving.

If you were arrested for DWI in Galveston County and police obtained your blood through a warrant, Zendeh Del & Associates, PLLC can review the circumstances of the warrant and blood evidence with you.

Contact our Galveston office to schedule a free consultation.

This article provides general information about Texas DWI cases and is not legal advice. The issues that may apply in a particular case depend on its specific facts.

Frequently Asked Questions About Texas DWI Blood Warrants

Can I refuse a blood warrant in Texas?

There is an important difference between refusing an officer’s request for a voluntary blood specimen and attempting to prevent officers from executing a court-authorized search warrant.

Texas’s implied-consent law addresses refusals, but Texas law also permits officers to obtain a warrant directing that a specimen be taken. Section 724.012 specifically recognizes obtaining a warrant as one basis for requiring a specimen in circumstances covered by that provision.

If police have obtained a valid warrant, physically resisting the blood draw can create additional problems and does not itself invalidate the warrant. Questions about whether the warrant or resulting evidence can be challenged should generally be addressed through the legal process.

How quickly can police obtain a DWI blood warrant?

There is no single amount of time that applies to every Texas DWI investigation.

The process depends on circumstances including the investigation, preparation and submission of the affidavit, availability of a magistrate, issuance of the warrant, transportation, and arrangements for the blood draw.

From a defense perspective, the important task is to establish the actual timeline and determine what happened at each stage.

Who can draw DWI blood?

Texas Transportation Code § 724.017 lists the people who may take a blood specimen at the request or order of a peace officer under Chapter 724. They include a physician, qualified technician, registered professional nurse, licensed vocational nurse, and certain authorized emergency medical personnel. The statute also states that the blood specimen must be taken in a sanitary place.

Can blood-test results be wrong?

Blood testing is scientific evidence, but that does not mean every reported result should be accepted without examining how it was produced.

Collection, identification, preservation, handling, laboratory procedures, analytical data, and interpretation can all warrant review depending on the facts of the case.

A defense investigation should therefore examine the underlying process rather than simply accepting the final number printed on a laboratory report.

Can a DWI blood test be thrown out?

In some cases, blood evidence can be suppressed or excluded, but there is no automatic rule that a particular defect results in exclusion.

Courts have suppressed results from unconstitutional warrantless blood draws, while courts have also upheld blood evidence when warrants were supported by probable cause or when other legal doctrines applied.

Whether a blood result can be excluded requires an analysis of the specific warrant, collection procedure, evidence, and applicable law.

Can I beat a DWI if my BAC was over .08?

A BAC over 0.08 is significant evidence because Texas law includes an alcohol concentration of 0.08 or more within its definition of intoxication.

But a laboratory result does not eliminate the State’s burden of proving the DWI charge beyond a reasonable doubt. The defense can still examine the legality of the investigation, the warrant, collection and handling of the blood, laboratory testing, timing of the draw, and what the evidence establishes about intoxication while operating the vehicle.

Zendeh Del & Associates’ published results include DWI cases with reported alcohol concentrations substantially above .08 that ended in acquittal or dismissal. Those outcomes do not guarantee similar results in another case, but they demonstrate why a DWI case should be evaluated on all of its evidence rather than a BAC number alone.