What Is Probable Cause for a DWI Arrest in Texas?

Two Standards — Stop and Arrest Are Separate

Texas DWI arrests require two separate constitutional standards. Reasonable suspicion — the lower standard — is needed to initiate the traffic stop. Probable cause — the higher standard — is required to make the arrest itself. A stop that satisfies reasonable suspicion can still produce an unlawful arrest if SAPD did not develop sufficient probable cause before taking the driver into custody. Both are independently challengeable at the Cadena-Reeves Justice Center.

Reasonable Suspicion to Stop

Reasonable suspicion requires a specific, articulable fact that a traffic violation or criminal activity has occurred or is occurring. For DWI stops on San Antonio’s IH-10, IH-35, Loop 1604, and the River Walk corridor, officers typically cite weaving within a lane, erratic speed, failure to maintain a single lane, or equipment violations. The standard is objective — what a reasonable officer would believe given the specific facts, not a subjective hunch.

Probable Cause to Arrest

Once stopped, SAPD must develop probable cause to arrest — enough specific, articulable facts to reasonably believe the driver is intoxicated. Officers build probable cause through the driver’s appearance (bloodshot or watery eyes, odor of alcohol, flushed face), statements made during the stop, and field sobriety test performance. Each element is independently challengeable:

• SFST results depend on strict protocol compliance — deviations invalidate the observations
• Subjective observations can be contradicted by SAPD dashcam and bodycam footage
• Statements made during a stop have specific legal protections

Why Both Standards Matter for Your San Antonio DWI Defense

A successful challenge to either standard collapses the case. If the stop lacked reasonable suspicion, nothing obtained during the stop is admissible — including the breath test result, the SFST observations, and the arrest itself. If the stop was valid but the arrest lacked probable cause, the DWI charges still fall. Our San Antonio DWI attorneys evaluate both independently on every case from the day we are retained.

Video Evidence and the Stop Analysis

SAPD officers wear body cameras and most SAPD patrol vehicles have dashcams. We obtain all footage the day we are retained and issue preservation demands before retention windows close. The gap between what the officer’s report describes and what the video actually shows is where the probable cause challenge begins. A report describing “strong odor of alcohol and slurred speech” contradicted by video showing normal speech is the foundation of a successful suppression motion at Cadena-Reeves.