When Police Need a Warrant to Take Your Blood

The Sequence Most People Are In

You refused the breath test. You thought that was the end of it. Twenty minutes later, an officer tells you a judge has signed a warrant and a nurse is going to draw your blood whether you agree or not.

This is not uncommon in Texas DWI cases. In major metropolitan counties like Dallas, judges are available around the clock to review electronic warrant requests, and the time between a driver’s refusal and the execution of a blood draw can be remarkably short. Understanding how this process works (and more importantly, where it can go legally wrong) is the starting point for any meaningful challenge to blood evidence obtained under a warrant.

Officers routinely seek a blood draw warrant after a refusal. They also seek one when they suspect drugs rather than alcohol, because a breath test only measures ethanol and blood is the only practical way to document controlled substances or prescription medications. And in cases involving an accident with serious injury or death, officers may seek a warrant as a matter of course, regardless of whether consent was offered. In Dallas County and other large Texas counties, officers submit electronic warrant affidavits to on-call magistrates who can approve them within minutes.

Blood Draws Are Searches

The reason a warrant is involved at all is that taking blood out of a person’s body is a search of that person, not a routine booking step. It reaches inside you, which is why it sits under the Fourth Amendment and under Article I, Section 9 of the Texas Constitution, and why the Code of Criminal Procedure requires probable cause supported by oath or affirmation before any warrant issues.

A blood warrant is an evidentiary warrant, issued to search for and seize items constituting evidence of an offense. The Code requires that sufficient facts be presented to the magistrate first, and that a sworn affidavit setting out substantial facts establishing probable cause be filed in every instance in which a search warrant is requested. The warrant is only as strong as that affidavit, and the affidavit either says enough or it does not.

McNeely

The authority to compel a blood draw was addressed by the United States Supreme Court in Missouri v. McNeely in 2013. Before that decision, some courts held that the natural dissipation of alcohol in the bloodstream created an automatic emergency justifying a warrantless draw. The Supreme Court rejected that.

Be precise about what the Court actually held, because the popular version of it overshoots. The question was whether the natural metabolization of alcohol presents a per se exigency in all drunk driving cases. The Court held that it does not, and that exigency in this context has to be determined case by case on the totality of the circumstances. It did not hold that alcohol dissipation can never support an exigency. It held that it does not do so automatically.

What that means in practice depends on where you were arrested. In a county running a round-the-clock warrant system, the State has a hard argument that a warrant could not have been obtained in time. In a rural county where warrants are not easily obtained, and particularly in a serious injury or death case, the State may be able to show exigency more readily.

Villarreal

McNeely is federal. Villarreal is what happened when the same question reached the Texas Court of Criminal Appeals.

In State v. Villarreal, the driver was arrested for DWI, had prior DWI convictions, and refused to consent to a blood test. There was no warrant, and the State conceded there were no exigent circumstances. The State’s argument was that the implied consent and mandatory blood draw provisions of the Transportation Code authorized the draw on their own.

The court rejected that. A nonconsensual search of a DWI suspect’s blood conducted under the mandatory blood draw and implied consent provisions, in the absence of a warrant or an applicable exception to the warrant requirement, violates the Fourth Amendment.

What remains permissible after Villarreal matters as much as what does not. The statutes are not void, and the mandatory draw provisions still describe circumstances in which an officer is required to seek a specimen. What Villarreal removed is the idea that those statutes by themselves excuse the warrant requirement. Consent still works if it was actual consent. Exigency still works if the State can show it on the facts. What no longer works is pointing at the statute and stopping there.

The Mandatory Draw Statute Today

Texas law lists situations in which an officer is required to take a specimen after an arrest and a refusal. The listed circumstances are a crash in which someone other than the driver died or suffered serious bodily injury, a passenger younger than fifteen in the vehicle, and certain prior intoxication convictions or community supervision, including a prior DWI with a child passenger, intoxication assault, or intoxication manslaughter, or two or more prior convictions for the base intoxication offenses.

Two things follow that people get wrong. First, the statute only applies to a person who has actually been arrested. Second, and more importantly, after McNeely and Villarreal the State still has to show either a warrant or a genuine exception. Being in a listed category does not make a warrantless draw lawful by itself.

One further detail from the same statute: the officer designates which specimen is taken, and for a mandatory draw Texas courts have held that one and only one specimen may be taken.

What refusing actually produces, and what it costs on the license side, is covered on Refusing the Test. What the implied consent statute obligates in the first place is covered on Implied Consent and the DIC-24.

What the Affidavit Has to Establish

A blood draw warrant must be supported by a sworn affidavit establishing probable cause, meaning specific, articulable facts that would lead a reasonable magistrate to conclude the driver was operating a motor vehicle while intoxicated. That is not a high standard, but it is a real one, and it is satisfied or not based entirely on what the affidavit actually says.

The phrase that matters is within the four corners. A magistrate reads the affidavit and nothing else. What the officer knew but did not write down, what the video would have shown, what the officer later testifies to at a hearing: none of that is what the magistrate had.

Where Affidavits Fail

This is where warrants are vulnerable in ways that are not obvious.

• Conclusory language. A magistrate must evaluate the facts stated in the affidavit, not the officer’s conclusions about them. The driver appeared intoxicated is a conclusion, not a fact. An affidavit built mostly on conclusions may not satisfy the Fourth Amendment.
• Boilerplate affidavits. In high-volume counties, officers sometimes use template affidavits filled in with minimal case-specific detail, where the description of the driver’s behavior is nearly identical across dozens of cases. Boilerplate that fails to reflect the particular facts can be constitutionally insufficient.
• Internal inconsistencies. An affidavit that calls the driver unsteady but also notes they completed the walk-and-turn, or claims a total refusal when video shows partial cooperation, contains contradictions that undermine the probable cause showing.
• Time and sequence problems. The affidavit’s facts must support probable cause at a point in time consistent with the timeline. If the facts reflect observations from much earlier in the encounter and intervening events are not accounted for, the connection weakens.
• Defects in the oath. An affidavit has to be sworn. Not signed: sworn, before someone. Texas courts have held that an officer’s failure to take an oath and swear to the facts renders defective any warrant issued on that affidavit, and that the oath must be made in the presence of another person rather than satisfied by the printed language on the form.

That last category is not theoretical, and it is being raised more often. In a 2025 Dallas case, an officer applied for a blood warrant on an affidavit whose form recited that he had appeared before an undersigned authority and had been duly sworn. No such authority was identified. The form carried a jurat with a signature line for a notary public, and the officer completed the jurat himself and left the notary line blank. No one administered an oath. The trial court suppressed the blood evidence, the State appealed, and the court of appeals affirmed, holding that the affidavit was unsworn and invalid and that the good-faith exception did not apply because any reasonable officer would have known the affidavit was not sworn.

Who May Draw and Where

Even a facially valid warrant can produce suppressible evidence if it was carried out improperly.

Who draws the blood. Texas law requires a qualified person, such as a physician, qualified technician, registered nurse, or licensed vocational nurse. A draw by an unqualified individual is not valid under the statute. Note one wrinkle: Texas courts have held that this statutory list governs draws taken at an officer’s request rather than draws taken under a search warrant, so the analysis in a warrant case runs through Fourth Amendment reasonableness instead.

Where the blood is drawn. The draw must occur under medically accepted conditions. Texas courts have held that a medical environment is ideal but not required, and that the question is whether the setting was a safe place in which to draw blood without an unjustified risk of infection or pain. An improvised draw in an unsuitable location raises reliability questions on top of the legal issue.

Scope of the warrant. A warrant authorizes a specific search. If it authorized a draw for alcohol testing and the lab also tested for controlled substances without separate authority, the extra testing may have exceeded the warrant’s scope.

Chain of custody. From the moment of the draw, the sample has to be documented through every transfer: the nurse to the officer, the officer to the evidence technician, the technician to laboratory intake. A gap anywhere in that chain, a missing signature, an inconsistent timestamp, or an unexplained storage interval, raises the question of whether the sample that was tested is the sample that was drawn from you.

No Refusal Weekends

An announced No Refusal weekend changes staffing and turnaround, not the law, and the authority to seek a blood warrant after a refusal exists every night of the year. The operational reality of those weekends is covered on No Refusal Weekends.

Challenging the Warrant

A warrant challenge is a legality argument, and that distinction matters more than it sounds like it should. It asks whether the blood was obtained lawfully. It has nothing to do with whether the laboratory measured correctly. The remedy is suppression, which removes the result from the case entirely, and it is pursued by motion, usually followed by a hearing at which the defense questions the affiant officer. That process is covered on Motion to Suppress. Your ALR hearing comes months earlier and puts the same officer under oath on the same facts, which is often where a defective affidavit first shows itself, so the transcript is worth having before the suppression hearing. See the ALR hearing.

The other route asks whether the science was sound and properly applied, is argued through an expert, and is covered on Challenging Expert Testimony and the Kelly Hearing. They are separate arguments with separate standards, and a case can carry both.

One Texas feature is worth stating accurately, because it is frequently overstated. Texas Code of Criminal Procedure Article 38.23 says evidence obtained in violation of the Constitution or the laws of the United States or Texas cannot be admitted. Texas has only one narrow good-faith exception, in Article 38.23(b): evidence is not suppressed when an officer relied in objective good faith on a warrant a neutral magistrate issued on probable cause. That exception is narrower than the federal doctrine, and it does not rescue a warrant whose affidavit never established probable cause, that was facially defective, that was never sworn, or that was obtained through false or misleading statements. Neither outcome is certain in any given case, but the officer’s good intentions alone do not cure those defects.

If the Warrant Stands, the Sample Still Can Be Attacked

The warrant analysis and the laboratory analysis are two separate fights that operate independently. Suppressing the warrant-based evidence is the most complete remedy because it removes the blood test entirely. But even when the warrant holds up, the laboratory result may still be contestable on scientific grounds: the tube, the preservative, the storage, the chain of custody, the calibration, the controls, and the chromatogram. Those challenges are set out on How Texas DWI Blood Results Get Challenged.

Getting the Warrant and Affidavit

None of this can be evaluated from memory of the night. The warrant and the affidavit are documents, and they have to be obtained and read line by line. Once a warrant has been executed, the affidavit is public information, and the magistrate’s clerk is required to make a copy available for public inspection during business hours.

What to obtain: the affidavit, the warrant itself, the return, the timestamps on each, the identity of the magistrate, the jurat and who signed it, and the video that either supports or contradicts what the affidavit describes. How that request is made in the criminal case is covered on Discovery.