What Is Probable Cause for a DWI Stop in Texas?

Two Standards: Reasonable Suspicion vs. Probable Cause

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 the officer did not develop sufficient probable cause before taking the driver into custody. Both are independently challengeable.

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 Austin’s I-35, MoPac, 6th Street, and Rainey Street, officers typically cite weaving within a lane, slow or 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 what a particular officer subjectively believed.

Probable Cause to Arrest

Once stopped, the officer 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. Importantly, each of these is independently challengeable: SFST results depend on protocol compliance, the officer’s subjective observations can be contradicted by dashcam video, and statements made during a stop have specific legal protections.

Why Both Standards Matter for Your Austin 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 Austin DWI attorneys evaluate both independently on every case.

Video Evidence and the Stop Analysis

APD officers wear body cameras and most patrol vehicles have dashcams. We obtain all footage the day we are retained. The gap between what the officer’s report describes and what the video actually shows is where the stop challenge begins. A report that says “weaving in lane” and a video that shows consistent lane position creates the basis for a suppression motion under Art. 38.23.