What Police Need to Pull You Over for DWI in Texas

What Reasonable Suspicion Requires

A traffic stop is a brief investigative detention, often called a Terry stop after Terry v. Ohio. To make one, an officer needs reasonable suspicion, meaning specific, articulable facts that suggest a traffic violation or criminal activity. A hunch is not enough. Common stated reasons include speeding, failure to signal, weaving or drifting, an equipment problem like a broken taillight, or a report of a possible impaired driver.

To move from a stop to an arrest, the officer needs probable cause, a higher standard built from the officer’s observations and your performance on field sobriety tests. The gap between those two standards is where many DWI cases are won. If the officer lacked reasonable suspicion to make the stop in the first place, everything that followed, including the tests, the statements, and the arrest, can be challenged and potentially thrown out under Texas Code of Criminal Procedure Article 38.23. Texas has no broad good-faith exception, so illegally obtained evidence is excluded even when the officer believed the stop was lawful.

One warning worth carrying into any conversation with a lawyer: Texas recognizes a general reasonable suspicion of DWI stop that does not depend on naming a specific traffic offense at all. It has become the standard answer when the stated traffic violation turns out to be weak, so a stop can survive even when the ticket does not.

The 24 Driving Cues

Officers are trained to detect impaired driving in phases, and the first phase is watching the vehicle in motion. The question the officer is answering in that phase is a narrow one: should I stop this driver?

The federal detection curriculum gives officers 24 visual cues for that decision. They fall into a few natural groups.

Trouble keeping the car in its lane. Weaving, weaving across lane lines, drifting, straddling a lane line, swerving, driving in opposing lanes or the wrong way on a one-way, and driving on something other than the designated roadway.

Trouble with speed and spacing. Unnecessary acceleration or deceleration, varying speed, driving 10 miles per hour or more under the limit, following too closely, and almost striking an object or vehicle.

Trouble with turns and stops. Turning with a wide radius, stopping problems, stopping in a lane for no apparent reason, an illegal or improper turn, and an improper or unsafe lane change.

Trouble responding. Slow response to traffic signals, slow or no response to the officer’s signals, stopping inappropriately in response to the officer, failure to signal or a signal inconsistent with the action, and driving without headlights at night.

The judgment calls. Inappropriate or unusual behavior, and appearing to be impaired.

Those last two are worth pausing on, because they are not really observations. They are conclusions, and they are the ones an officer reaches for when the video does not show anything on the rest of the list.

Speeding Is Not One of Them

Speeding by itself is not on NHTSA’s list of impairment cues. Alcohol tends to slow reactions, not make people drive faster, and driving well under the limit is actually a listed cue. So while speeding may justify the stop, it is weak evidence on its own that you were intoxicated.

That distinction does real work. A stop for speeding is a lawful stop. It is not, by itself, a reason to suspect intoxication, and officers trained in the curriculum will concede the point on cross-examination, because it is in their own manual.

There is a related weakness in how speed gets written up. Where a report says only that a driver was traveling at a high rate of speed, without an actual speed, without a comparison to the posted limit, and without saying how the speed was measured, at least one Texas court has treated that allegation as conclusory.

Weaving Within Your Own Lane

This is the question people ask most, and the honest answer is that it depends on the court you are in.

Texas law says a driver on a road divided into marked lanes shall drive as nearly as practical entirely within a single lane, and may not move from the lane unless the movement can be made safely. Texas courts are split on what the State has to prove. Some read the statute as creating one offense, moving out of a marked lane when it is not safe to do so, which means a slow drift into another same-direction lane does not support a stop without evidence the movement was unsafe. Others read it as two independent ways to violate it. The Court of Criminal Appeals split four to four on the question, so the opinion discussing it is not binding.

Crossing the fog line is its own question. The fog line is the boundary between the lane and the shoulder, and Texas limits use of an improved shoulder to seven listed purposes, including stopping, decelerating before a right turn, and avoiding a collision. Merely driving on an improved shoulder is not automatically evidence of an offense, and in at least one case an officer who stopped a driver for it could not prove the movement was unsafe.

Leaving a Bar Is Not a Violation

Coming out of a bar parking lot is not a crime, and it is not a traffic violation. An officer who watches you walk to your car and drive away has watched you do something completely legal.

What that surveillance produces is a reason to follow you, and the follow is where the officer looks for one of the 24 cues or an ordinary moving violation. So the bar did not justify the stop. Something in the next half mile did, or the officer will say it did, and that is the piece worth examining on video.

Anonymous Tips

A call to police is a starting point, not a stop. Texas courts look at what the caller actually reported, how specific it was, whether the officer corroborated any of it before acting, and whether the officer’s own observations added anything.

There is a second layer that surprises people. Not every police contact is a stop at all. Courts sort police encounters into three kinds: consensual encounters that do not implicate the Fourth Amendment, investigative detentions that require reasonable suspicion, and arrests that require probable cause. Texas courts have found the encounter consensual in cases that felt like anything but, including an officer who pulled in behind a parked car and turned on his overhead lights and spotlight. Emergency lights are not automatically a detention. The label matters because the burden follows it: a defendant has to first show a seizure happened without a warrant before the State has to justify it.

How Long a Stop Can Last

There is no clock. The Supreme Court has expressly rejected rigid time limits on investigative stops, so nobody can tell you a Texas DWI stop becomes unlawful at 20 minutes or at an hour.

What the law asks instead is whether police diligently pursued a means of investigation likely to confirm or dispel their suspicions quickly, and the State carries the burden of showing the detention was limited in scope and duration. A stop justified only by an observed traffic violation becomes unlawful if it is prolonged beyond the time reasonably required to complete the mission of writing the ticket. Once the original purpose is finished, continued detention is permitted only if there is reasonable suspicion of another offense.

Waiting for the DWI Officer

This version of the question is common in North and Central Texas, because several agencies dispatch a dedicated DWI unit rather than let the patrol officer work the case.

The honest answer is that Texas courts have generally upheld those waits. Delays have been found reasonable where they served a legitimate law enforcement purpose, including letting a DWI enforcement officer take over so the officer who made the stop can return to patrol, waiting for a video camera so the tests can be recorded per department policy, and waiting for a rookie officer who needs the training.

The defense argument is narrower than “it took too long.” If the officers on scene were themselves certified to give the tests, if none of them left to return to patrol after the specialist was called, and if the wait produced no net gain in patrol coverage, then the delay did not serve the purpose the State is claiming for it. That argument lives or dies on what the officers actually did during the wait, which is why the video and the dispatch log matter more than the stopwatch.

What the Officer Does Next

Once you are stopped, the conversation at the window is the investigation. Officers are taught that they need a factual basis to ask a driver to step out, and the usual list is the odor of alcohol, bloodshot eyes, slurred speech, fumbling for the license, and an admission of drinking.

A common technique is to ask for two things at once, like your license and your insurance, while also asking a distracting question such as where you are coming from. The goal is to divide your attention. Fumbling or a slow answer then gets written down as a clue.

Two things typically follow. The officer asks you to perform field sobriety tests, which are voluntary in Texas. And the officer may offer a roadside portable breath test. That device is not certified in Texas to give a reliable alcohol concentration, and its number is not admissible to prove your BAC, but a result near or over the limit will usually get you arrested anyway. What to actually say and do at the window, and how to decline those tests without escalating the encounter, is on what to do when you are pulled over.

When the Stop Becomes an Arrest

A lawful stop does not make an arrest lawful. Those are two separate legal questions with two different standards, and the arrest question has its own page: what police need to arrest you for DWI.

Was Your Stop Legal?

The answer is on the video, not in anyone’s memory. Compare the driving the officer described in the report to the driving the dashcam actually shows, because officers who activate their lights before recording never capture the weaving they describe. The mechanics of getting that footage before it is overwritten are on video and evidence preservation, and the procedural vehicle for challenging a bad stop is a motion to suppress.

Checkpoints Are Not a Thing in Texas

Texas does not run sobriety checkpoints, and a stop that functioned like one still has to be justified against you individually. See DWI checkpoints in Texas.