San Antonio DWI Lawyer: Understanding the Three DWI Detection Phases
If police arrest you for DWI in San Antonio, Texas, then learning how police make a case against you is the first step towards building a strong defense. I am an experienced San Antonio DWI lawyer and I have helped countless clients challenge drunk driving charges in Bexar County.
In this post, I will describe the three DWI detection phases and why they are fundamental to a drunk driving defense.
How Police Find DWI Motorists in San Antonio: The Three-Phase Process
Police in San Antonio and throughout Texas follow a three-step test to help them stop and arrest suspected drunk drivers. The test is:
- Vehicle in Motion – Police watch your driving behavior and look for clues that you are impaired
- Personal Contact – Officers interact with you and look for classic telltale signs you are intoxicated
- Pre-Arrest Screening – Officers administer standardized field sobriety tests (SFSTs)
Notably, police in San Antonio capture all this evidence with both their body and dash cameras. Prosecutors then use this evidence, along with your breath or blood BAC test, to prove to a jury that you were DWI when police arrested you.
Phase One: Vehicle in Motion – Why did police pull you over?
The first question a San Antonio DWI lawyer asks in every case is: “Did the officer have a legal reason to pull you over?” The Fourth Amendment requires police to have reasonable suspicion to pull you over. If they did not have legal grounds to stop you, then you can file a motion to suppress and ask a judge to throw out your case.
Common Traffic Violations Leading to DWI Stops
However, reasonable suspicion is a low standard. For example, police can stop you for the following reasons:
- Speeding
- Driving with an expired registration
- Having a burned out brake light
- Weaving within a lane
- Following another car too closely
Critically, sober drivers and drunk drivers commit these traffic violations every day. If police stop you for a minor traffic violation rather than an obvious sign of drunk driving, then this becomes a powerful defense point. This is especially true if you look normal on the arrest video and have a borderline breath test result.
The 24 DWI Detection Cues Police Use in San Antonio
The National Highway Traffic Safety Administration (NHTSA) identifies 24 driving behaviors that may show the driver is intoxicated. They fall into four categories.
Problems Maintaining a Proper Lane:
- Weaving or zigzagging
- Crossing lane lines without signaling
- Straddling lane markers
- Swerving abruptly
- Making a wide turn
- Drifting at an angle
- Nearly hitting objects or other vehicles
Speed and Braking Issues:
- Stopping problems (too far, too short, or making jerky stops)
- Accelerating or decelerating rapidly
- Varying your speed
- Driving well below the speed limit
Vigilance Problems:
- Driving in the opposite lane or the wrong way on a one-way street
- Delaying your response to traffic signals
- Failing to respond to the officer’s stop signals
- Stopping in a lane without a reason
- Driving without headlights at night
- Improperly using or missing a turn signal
Judgment Problems:
- Tailgating
- Making an unsafe lane change
- Making an illegal turn
- Driving on shoulders or non-roadway areas
- Stopping inappropriately in response to police lights
- Showing unusual behavior (drinking in the car or acting strange)
How We Build your DWI Defense from Phase One
The 24 cues listed above are common in drunk driving cases and often show that the driver was DWI when police pulled him over. However, everyday motorists commonly exhibit these cues too. For instance, people sometimes swerve unexpectedly to avoid a pothole, to adjust the radio, due to a momentary distraction from a passenger, or because the driver is checking the GPS coordinates on their route.
This is a key point because it offers an innocent explanation for bad driving. And a DWI lawyer in Bexar County can use these facts to lay the groundwork for a not guilty verdict at trial.
Phase Two: Personal Contact – What Officers Look for During a DWI Traffic Stop
After a San Antonio police officer pulls you over, they switch into phase two. Here, they look for signs you are intoxicated. Namely, police watch the driver and look for the following signs:
Common DWI Indicators Police Look For after the traffic Stop:
- Bloodshot or watery eyes
- Odor of alcohol coming from the driver or vehicle
- Slurred speech
- Fumbling for a driver’s license or insurance card
- Difficulty exiting the vehicle
- Swaying or an unsteady balance
- Slow responses to police questions
- Inconsistent answers
- Soiled clothing
- Open alcohol containers
The Defense Perspective
Police often make subjective judgements when they smell alcohol on a driver’s breath. In particular, officers fall victim to confirmation bias – they smell alcohol and quickly stop looking for signs of sobriety.
To illustrate, sober people do the following during a traffic stop:
- Answer police questions coherently and without slurring their words
- Get out of the car without a problem
- Behave normally under the circumstances.
On top of that, there are many factors that mirror symptoms of intoxication:
- Fatigue from a long work day
- Being nervous or anxious about the traffic stop that cause the driver to fumble for a driver’s license or proof of insurance
- Medical conditions like a bad back, bad knees, or age that cause the driver to struggle to get out of the car
- Allergies causing red eyes
- Speech patterns or accents that vary from driver to driver
An experienced San Antonio DWI lawyer will point these facts out to the jury. More importantly, these small details will help your lawyer rebut the officer’s subjective opinion that you were driving drunk.
Phase Three: Field Sobriety Tests in San Antonio DWI Cases
If the police officer moves into phase three, then this is a major red flag that the officer thinks you are intoxicated. This happens when the officer asks you to perform Standard Field Sobriety Tests (SFSTs). The three tests listed below will become a major part of the State’s evidence against you at trial.
Horizontal Gaze Nystagmus (HGN) Test
Officers hold a pen or object 12 to 15 inches from the person’s nose and ask the person to follow the pen’s movement with their eyes. Of major interest, police look to see if the person’s eyes jerk or move involuntarily during the test. Furthermore, they look for three clues per eye or six total clues. If the officer sees four or more clues, then the SFST guidelines say the driver failed the test.
HGN Test Clues (The Eye Test)
- First, the officer will prescreen you to make sure they can perform the HGN test on you
- Then they check your eyes for lack of smooth pursuit, i.e., they check if your eyes bounce or vibrate while you follow the pen or tracking object
- Next, they check for nystagmus at maximum deviation, i.e., they move the pen or stimulus to an extreme angle and then check to see if your eye jerks or bounces around
- Finally, they move the pen or stimulus at a certain speed to a 45 degree angle and check to see if your eyes jerk or bounce before they reach the 45 degree angle (Does your eye bounce too soon?)
Basic Defense Strategy : Police officers must follow specific rules and procedures when they perform this test on a suspected drunk driver. If police do not do the test correctly, then your San Antonio DWI lawyer can move to suppress the HGN test. See Emerson v. State, 880 S.W.2d 759, 761 (Tex. Crim. App. 1994).
Walk – and – Turn (WAT) Test
This is a divided attention test. It requires the driver to first listen to instructions and then perform a test. Specifically, the test requires a driver to:
- Stand heel-to-toe on a line while the driver listens to the officer’s instructions
- The driver then takes nine (9) heel-to-toe steps forward
- Turns in a specific manner
- Take nine (9) heel-to-toe steps back
- While doing this test, the driver must keep his hands by his sides
- And the driver must count the steps out loud
Police look for eight clues during this test. If the driver shows two or more clues, then he failed the test.
Walk-and-Turn Clues:
- Cannot maintain balance while listening to the officer’s instructions
- Starts before the officer tells him to begin
- Stops while walking
- Fails to touch heel-to-toe during the test (A person does not touch heel-to-toe if there is more than a .5 inch gap between the steps)
- Steps off an imaginary line
- Uses arms for balance (This clue counts if the person raises his arms more than 6 inches from his sides)
- Makes an improper turn
- Takes the wrong number of steps
Defense Considerations: The test is tough to do perfectly even under ideal conditions. Worse yet, if you have bad knees, a bad back, are overweight, or if you have a medical condition, then this can cause you to fail the test even if you are sober.
One-Leg Stand (OLS) Test
This test begins with your feet placed together. From there, you raise one foot six inches off the ground and then count out loud for 30 seconds. If you show two or more clues, then you failed this test.
One-Leg Stand Clues:
- Swaying while balancing
- Using your arms for balance (if you raise or move your arms more than 6 inches from your sides)
- Hopping to maintain balance
- Putting your foot down before 30 seconds
Why this test is unreliable: DWI defense lawyers will show the jury that standing on one foot for 30 seconds is not normal or typical behavior for most people. Equally important, many people are nervous during this test because they are afraid they will go to jail if they fail. And, not all roads or pavements are flat or level. In short, a person can fail this test and still be sober.
Breathalyzer and Blood Tests in San Antonio DWI Cases
Breath Tests
After San Antonio police arrest you for DWI, they will ask you to provide a sample of your breath. If you refuse, then DPS will automatically suspend your driver’s license after 40 days. This is because Texas’s Implied Consent law requires you to provide a breath or blood sample if police arrest you for a DWI crime in Texas.
15-day DWI Arrest Rule
Of major interest, you have 15 days from the date of arrest to request an ALR hearing to challenge the license suspension. Otherwise, DPS will suspend your license, and you will give up the right to challenge the license suspension. Your San Antonio DWI lawyer can help you with the ALR hearing.
Blood Draws
If you decline to give a breath test, then SAPD or BCSO will likely get a warrant to draw your blood. This is one of the biggest changes in Texas DWI law in the last 15 to 20 years. In the early 2000s and before, you could decline the breath test and police would not get a warrant to draw your blood. This made it harder for prosecutors to prove the driver was over the limit at the time of his arrest.
Now, blood draws are standard in Bexar County, Texas. This means that if you decline a breath test, then police will get a blood draw. This difference is subtle, but carries major DWI defense implications.
As your proven and experienced DWI lawyer, I have the experience to challenge breath and blood tests in court.
Immigration Consequences of a DWI Conviction in Bexar County, Texas
The Supreme Court requires your Bexar County DWI lawyer to advise clients who are not US Citizens about the immigration consequences of a DWI conviction. See Padilla v. Kentucky, 559 U.S. 356, 359 (2010). For this reason, my office will consult with your immigration attorney if you are a Legal Permanent Resident (LPR), have political asylum, or are in the process of getting status to stay in the country. At any rate, we will never let a client – who is not a US Citizen – plead guilty to a DWI crime without first consulting with an immigration attorney.
Why You Need an Experienced and Proven DWI Lawyer
DWI arrests can cause problems even for a misdemeanor first-time offenders:
- Possible jail time
- Reporting to a probation officer
- Paying fines and court costs
- Getting your driver’s license suspended
- Losing a job
- And having a criminal record
Many clients I represent are first-time DWI offenders. They have clean records. And most of them are charged with a misdemeanor offense. In contrast, other clients are repeat offenders who are facing heavier penalties.
My goal in each of these cases is to make sure the criminal justice system treats them fairly. I do this by reviewing each case for the issues we talked about earlier. After that, I work with each client to reach the best results possible in their case.
Call a San Antonio DWI Lawyer Today. 210-733-7575
If you have a DWI case or a DWI MTR in San Antonio or Bexar County, then call or email me today. I am an experienced DWI lawyer. And I offer free and confidential consultations for every client.
About the Author: Your San Antonio DWI Advocate Genaro R. Cortez
When you are arrested for DWI in Bexar County, the legal system can feel overwhelming and indifferent. I am a dedicated San Antonio DWI lawyer who believes that every client deserves a rigorous, detail-oriented defense.
As a solo practitioner, I personally handle every aspect of your case. From the moment we meet for your free consultation, you will work directly with me—not an assistant or a junior attorney. My goal is to protect the rights of motorists facing a DWI charge in San Antonio.
Whether this is your first-DWI offense or you are a repeat offender, I will make sure you are treated fairly and pursue the best outcome for your future.