Managing Attorney
In Texas, law enforcement officers routinely seek blood samples in DWI (Driving While Intoxicated) cases, especially when a driver refuses to submit to breath testing or is involved in an accident. While a blood test can be one of the most powerful forms of evidence in a DWI prosecution, the legality of the blood draw hinges on whether the search and seizure of a suspect’s blood complied with the Fourth Amendment. This means a properly obtained and executed search warrant is usually required.
Understanding how warrants are obtained—and more importantly, how they can be challenged—is essential in defending against DWI charges. A successful challenge to a blood draw warrant can result in the suppression of the blood test results, often leaving the prosecution with a severely weakened case.
How Warrants Work in DWI Blood Draws
A warrant authorizing the seizure of a person’s blood must be supported by probable cause and issued by a neutral magistrate. Typically, an officer will submit an affidavit outlining the reasons they believe the suspect is intoxicated—citing facts like poor driving, odor of alcohol, slurred speech, field sobriety test results, or refusal to submit to breath testing. The magistrate then determines whether probable cause exists to justify a blood draw.
Texas law allows for telephonic or faxed warrants, making it easier for officers to obtain one quickly. Once issued, the warrant authorizes a medical professional to draw a blood sample in a medically approved setting.
However, just because a warrant is issued doesn’t mean it’s valid or immune from legal attack. Defense attorneys routinely scrutinize the warrant process to determine whether a client’s constitutional rights were violated.
Common Ways Blood Draw Warrants Are Challenged
1. Lack of Probable Cause in the Affidavit
A warrant must be supported by specific and articulable facts—not just boilerplate language or conclusory statements. If the affidavit fails to establish a clear connection between the suspect’s behavior and probable intoxication, it may not support probable cause. For example, vague claims such as “the driver appeared intoxicated” without citing specific observations like glassy eyes, odor of alcohol, or erratic driving may render the affidavit deficient.
Additionally, if the affidavit relies on unreliable sources or fails to explain how the information was obtained, it may be challenged for failing to establish a substantial basis for probable cause.
2. Stale or Incorrect Information
Even if an affidavit contains strong facts, those facts must be timely. Information that is too old or not clearly linked to the time of the alleged offense may be considered “stale,” undermining the warrant’s validity. Also, any material factual errors—such as misstating the time of arrest, misidentifying the suspect, or mischaracterizing events—can be grounds to suppress the blood evidence.
3. Improperly Administered Affidavit or Oath
In Texas, a warrant affidavit must be sworn to under oath. If the officer signs the affidavit but no oath is properly administered—either in person or telephonically—the warrant is defective. Courts have thrown out warrants where the jurat was present but the formalities of administering the oath were skipped.
4. Warrants Based on Reckless or False Statements
If an officer knowingly includes false information or recklessly disregards the truth in the affidavit, the defense can request a Franks hearing. If it’s shown that the false information was necessary to establish probable cause, the entire warrant may be invalidated. A successful Franks challenge requires a specific showing, often supported by contradictory records, bodycam footage, or witness testimony.
5. Failure to Follow Statutory Procedures
Even if the warrant itself is valid, the actual execution of the blood draw must comply with legal standards. Blood draws must be conducted by qualified medical personnel in a sanitary setting. If the draw is performed by someone not authorized under Texas law or in a manner that creates unnecessary risk or trauma, the defense may argue that the search was unreasonable.
6. Exceeding the Scope of the Warrant
Sometimes, a warrant may authorize only the seizure of blood, but law enforcement proceeds to conduct tests or retain samples for uses not permitted by the warrant. Courts have recognized that the seizure and testing of blood are two distinct Fourth Amendment events. If the warrant doesn’t explicitly permit testing—or if the testing exceeds its scope—the defense may have grounds to challenge.
What Happens if a Blood Draw Warrant Is Successfully Challenged?
When a judge finds that a blood draw warrant was issued or executed in violation of the Fourth Amendment or Texas law, the blood evidence can be suppressed. This means it cannot be used by the prosecution at trial. In DWI cases—particularly those involving no accident, no breath test, and no strong admissions—losing the blood evidence may leave the State with insufficient evidence to prove intoxication beyond a reasonable doubt.
In some cases, suppression of the blood result can lead to a full dismissal. In others, it may provide leverage for a favorable plea deal to a lesser charge like obstruction of a highway. And in all cases, it undermines the prosecution’s most scientifically compelling piece of evidence.
The Bottom Line for Texas DWI Defense
Challenging a blood draw warrant is a powerful defense tool in DWI cases. A successful suppression can dramatically shift the balance of power in favor of the defense. These challenges require a deep understanding of warrant procedures, evidentiary standards, and constitutional protections under both the U.S. and Texas Constitutions.
Ceja Law Firm thoroughly investigates the circumstances surrounding every blood draw in a DWI case. By dissecting the affidavit, reviewing bodycam footage, cross-examining officers, and scrutinizing lab reports, the firm works to expose constitutional violations that can result in critical evidence being thrown out.
If you or someone you know has been arrested for DWI involving a blood draw, it’s essential to speak with an experienced attorney who understands how to challenge the legality of the warrant and fight to protect your rights.
