The Importance of a Probable Cause Affidavit in Texas Criminal Defense

If you asked most criminal defense attorneys to rank the most important documents in a drug possession or sexual assault case, you’d probably hear about the indictment, offense report, lab results, body camera footage, or witness statements. While all of these matter, I believe one document stands above the rest: the probable cause affidavit.

As a Dallas criminal defense lawyer who regularly handles possession of controlled substances, distribution cases, and sexual assault charges, I’ve seen firsthand how a careful review of the probable cause affidavit can make or break a case. In fact, I’ve gotten serious felony cases dismissed and prevented charges from ever being filed—simply by scrutinizing this often-overlooked document.

A Real Case: First-Degree Felony Dismissed with One Email

Let me give you a concrete example. I once represented a client charged with first-degree felony possession with intent to deliver cocaine in Dallas County. Police had executed a search warrant at his apartment and found a substantial amount of cocaine, marijuana, and THC wax. The case seemed serious—my client faced significant prison time.

To defend this case, I did two simple things:

1. I carefully read the search warrant probable cause affidavit
2. I sent a detailed email to the prosecutor handling the case

The result? The case was dismissed.

Here’s what I found when I examined the probable cause affidavit. The affidavit established only two facts:

• My client had sold marijuana to a cooperating witness at a location OTHER than his residence—one full month before the search warrant was executed
• My client lived at the residence that police searched

That was it. Nothing more.

In my email to the Assistant District Attorney, I explained why this affidavit failed to establish probable cause. Under Texas law, there must be evidence—beyond mere conjecture—that the property being searched probably contains evidence of a crime at the time the warrant is issued. See Hass v. State, 790 S.W.2d 609, 611 (Tex. Crim. App. 1990).

The affidavit was missing critical information:

• No statement from the informant that drugs were inside the residence
• No surveillance on the residence showing drug trafficking activity
• No evidence my client left the residence with drugs in his possession
• No evidence my client was even living at the same address when he met the informant a month earlier

Without this connecting evidence, the search warrant lacked probable cause. Despite the drugs found during the search, the Mesquite Police Department’s case fell apart. The charges were dismissed.

Strategic Use of Probable Cause Affidavits in Sexual Assault Cases

In sexual assault investigations—including date rape cases, cases involving intimate partners, or allegations arising from consensual encounters—the probable cause affidavit can be equally powerful as a defensive tool.

Here’s a strategy I’ve used successfully multiple times to obtain grand jury no bills in Dallas County, Denton County, and Collin County:

Forcing Police to Create a Detailed Affidavit

When DNA evidence is critical to the state’s case, police detectives will typically try to obtain a DNA sample from the suspect. In sexual assault investigations, this often happens after a SANE exam (Sexual Assault Nurse Examiner) has been performed and DNA evidence has been collected from the alleged victim.

At this stage, the detective has usually conducted an extensive investigation in complete secrecy—interviewing witnesses, collecting digital evidence, and building their case—all before the suspect even knows they’re under investigation.

When the detective is ready to collect the suspect’s DNA, they’ll often approach the person and politely request a buccal swab (a cheek swab). Many people comply without understanding the implications.

But when my client refuses this voluntary request, the detective has no choice: they must obtain a search warrant for the DNA sample. And to get that warrant, they must swear out a probable cause affidavit containing all the evidence they have at that point in time.

This affidavit then becomes public record (unless sealed, which is rare in state cases). Once I obtain a copy of that affidavit, I can:

• Conduct my own investigation based on the evidence disclosed
• Direct my private investigator to interview the witnesses listed
• Arrange for my client to take a polygraph examination
• Present exculpatory evidence to the grand jury to seek a no bill

If the polygraph doesn’t work out for any reason, it remains protected by attorney-client privilege. But if my client passes, I can use those results—combined with the information from the affidavit—to demonstrate innocence at the grand jury stage and potentially prevent charges from ever being filed.

I’ve used this exact strategy to obtain grand jury no bills in multiple sexual assault cases across North Texas.

What Is a Probable Cause Affidavit?

Both the United States Constitution and the Texas Constitution protect individuals from unreasonable searches, seizures, and arrests. The Fourth Amendment to the U.S. Constitution states:

“The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.”

Texas has similar protections in Article I, Section 9 of the Texas Constitution, and Texas Code of Criminal Procedure Article 18.01(b) requires that “a sworn affidavit setting forth substantial facts establishing probable cause shall be filed in every instance in which a search warrant is requested.”

In practice, a probable cause affidavit is a sworn statement by a law enforcement officer—whether a Dallas police officer, a Texas Ranger, or an FBI agent—detailing their reasons for believing:

• There are sufficient grounds to arrest someone for a criminal violation, or
• There is probable cause to search property and seize items that may be evidence of a crime

The affidavit must establish that “the facts stated are sufficient in themselves to warrant a man of reasonable caution in the belief that an offense has been or is being committed.” Brinegar v. United States, 338 U.S. 160, 176-77 (1949).

Procedural Requirements: Form Matters

A probable cause affidavit isn’t just about what it says—it’s also about whether it was properly executed. The affidavit must meet strict procedural requirements:

• The affiant (officer) must sign the document
• The affiant must swear an oath as to its truthfulness
• The oath must be administered before a magistrate or other qualified official

As the Texas Court of Criminal Appeals has emphasized, these requirements have been the law “for the better part of a hundred years.” Clay v. State, 391 S.W.3d 94, 98-99 (Tex. Crim. App. 2013).

The Wheeler Case: When Officers Skip the Oath

Consider Wheeler v. State, 573 S.W.3d 437 (Tex. App.—Fort Worth 2019), a DWI case that illustrates how procedural failures can invalidate an entire search.

In Wheeler, a police officer arrested the defendant for driving while intoxicated. When Wheeler refused field sobriety and breath tests, the officer obtained a search warrant to draw his blood. The officer used a standard probable cause affidavit form to support the warrant request.

The problem? The officer never took the oath. He never swore to the affidavit before a magistrate.

The defense attorney filed a motion to suppress, and both the trial court and the appellate court agreed: without a proper oath, the affidavit was constitutionally invalid. All evidence obtained from the blood draw was suppressed.

The prosecution tried to invoke the “good faith exception” under Texas Code of Criminal Procedure Article 38.23(b), arguing the officer’s failure was an honest mistake. The Texas Court of Criminal Appeals rejected this argument.

The court held that officers must act in “objective good faith,” meaning a reasonable officer in the same position would have believed the warrant was valid. Because the oath requirement is so fundamental—codified in statutes, emphasized in case law, and taught in police academies—no reasonable officer could believe a warrant based on an unsworn affidavit was valid.

As the court explained, “it was wholly unreasonable for any officer” to ignore a constitutional mandate that has existed for over a century. Wheeler v. State, 626 S.W.3d 856, 863-64 (Tex. Crim. App. 2021).

Substantive Challenges: What the Affidavit Says

Beyond procedural defects, the content of the probable cause affidavit itself can be challenged. Courts are “bound by the four corners of the affidavit,” meaning they can only consider what’s actually written in the document—nothing more. Illinois v. Gates, 462 U.S. 213, 238 (1983); State v. McLain, 337 S.W.3d 268, 272 (Tex. Crim. App. 2011).

This creates opportunities for the defense when affidavits are vague, conclusory, or based on unreliable information.

The Duarte Case: Unreliable Informants

In State v. Duarte, 389 S.W.3d 349 (Tex. Crim. App. 2012), a San Antonio police detective submitted a two-page probable cause affidavit based primarily on information from a confidential informant—someone with pending criminal charges who wanted leniency in exchange for providing tips.

The defense challenged the affidavit, arguing it contained insufficient facts to verify the informant’s reliability or the accuracy of their information.

The Texas Court of Criminal Appeals agreed:

“We agree with the State that ‘an affiant’s basis for finding the informant reliable need not be of any certain nature.’ But, whatever its nature, it must be demonstrated within the four corners of the affidavit. Here, the affiant-officer believed that the confidential informant was credible largely because he was a ‘confidential informant’—a ‘snitch’ with pending criminal charges who wanted to trade a tip for leniency. We decline to equate the reliability of a first-time, unnamed informant with that of a named citizen-informant.”

The court held that the affidavit contained “insufficient particularized facts” to establish probable cause. The trial court’s decision to grant the motion to suppress was affirmed. Duarte, 389 S.W.3d at 360.

This case demonstrates an important principle: boilerplate language and bare conclusions aren’t enough. The affidavit must contain specific, verifiable facts that justify the search or arrest.

Why This Matters in Drug Cases

In possession of controlled substances and distribution cases, probable cause affidavits are often based on:

• Controlled buys by confidential informants
• Surveillance of suspected drug trafficking locations
• Traffic stops that lead to vehicle searches
• Information from anonymous tips

Each of these scenarios presents potential weaknesses in the probable cause affidavit:

• Was the informant reliable? How do we know?
• Did surveillance actually show drug activity, or just normal comings and goings?
• Was there a valid basis for the traffic stop and subsequent search?
• Was the anonymous tip sufficiently corroborated?

As my dismissed cocaine case demonstrates, even when drugs are found, the search can be unconstitutional if the affidavit doesn’t establish a sufficient connection between the place searched and the criminal activity alleged.

Common Defects in Probable Cause Affidavits

Through years of practice defending drug and sexual assault cases in Dallas County and surrounding areas, I’ve identified several recurring problems in probable cause affidavits:

1. Lack of Temporal Connection

Affidavits often fail to establish that evidence is likely to be found at the location at the time of the search. As in my dismissed case, showing a drug transaction occurred somewhere else weeks or months earlier doesn’t establish probable cause to search a residence now.

2. Stale Information

Information that is too old may not support a finding of probable cause, especially in drug cases where contraband is mobile and quickly consumed or distributed.

3. Unreliable Hearsay

Affidavits can include hearsay, but the source must be shown to be reliable through specific facts—not just conclusory statements like “this informant has been reliable in the past.”

4. Conclusory Statements

Statements like “based on my training and experience, this is consistent with drug trafficking” without specific supporting facts are insufficient. The affidavit must contain particularized evidence, not general conclusions.

5. Procedural Failures

As Wheeler demonstrates, even basic procedural requirements like taking the oath are sometimes overlooked, providing grounds for suppression.

The Defense Lawyer’s Role

When I take on a possession of controlled substances, distribution, or sexual assault case, reviewing the probable cause affidavit is one of my first priorities. I look for:

• Procedural defects—was the affidavit properly sworn and executed?
• Substantive weaknesses—does the affidavit actually establish probable cause?
• Reliability issues—are confidential informants properly verified?
• Temporal problems—is the information stale or insufficient to show current criminal activity?
• Missing nexus—is there a sufficient connection between the place searched and the alleged crime?

Many defense attorneys focus primarily on the evidence found during a search or the strength of witness statements. But if the probable cause affidavit that authorized the search or arrest is constitutionally deficient, none of that evidence may be admissible.

As one Texas court noted, the probable cause affidavit is “critical” to the validity of any search warrant. Without a valid affidavit, the warrant fails—and with it, the prosecution’s case.

Conclusion: Don’t Overlook the Foundation

If you’re facing drug charges or a sexual assault allegation in Dallas or the surrounding counties, the probable cause affidavit in your case deserves immediate, thorough review. This document may be the key to your defense—whether through:

• Getting evidence suppressed due to an invalid search or arrest
• Obtaining information needed to conduct an effective investigation
• Presenting exculpatory evidence at the grand jury stage
• Negotiating a favorable resolution with prosecutors

From a criminal defense lawyer’s perspective, underestimating the importance of the probable cause affidavit is a critical mistake. In many cases, this single document holds the key to the entire defense strategy.

Don’t wait to have your case analyzed. The sooner we can review the probable cause affidavit and other foundational documents in your case, the better positioned we’ll be to fight for your rights and your freedom.

Related Resources

For more information on related topics, see our articles on What is Probable Cause for Police to Arrest in Texas? and Illegal Search Warrants: Challenging The Underlying Affidavit.