San Antonio, Texas, has had its fair share of DWI arrests over the years, including some pretty high-profile cases. One such incident still fresh in our memory was the early 2024 arraignment of District 10 Councilmember Marc Whyte.
Mr. Whyte pleaded out of the DWI charges in exchange for a six-month alcohol-free probation, an $850 fine, and a mandatory DWI education course. However, his widely publicized case underscored just how DWI, an offense widely dismissed as inconsequential, can have far-reaching repercussions on an individual’s career and reputation.
Most DWI arrests are typically preceded by field sobriety tests. These practical assessments enable law enforcement officers to evaluate your level of physical and mental impairment before possibly making an arrest.
But are field sobriety tests mandatory, and what are my rights as a defendant?
This article shall endeavor to put those questions into perspective. Below is what a San Antonio DWI attorney would want you to know about field sobriety tests.
What Is DWI?
DWI (Drinking While Intoxicated) is the crime of operating a motor vehicle while under the considerable influence of alcohol, impairing drugs, or both.
DWI accounts for a substantial percentage of motor vehicle-related offenses in San Antonio, Texas. Therefore, it’s imperative to understand your rights as a defendant following a DWI arrest.
A good place to kick-start your defense is by contacting a San Antonio DWI attorney. The lawyer will quickly visit the precincts where you’re being held up and bring themselves up to speed with the facts of your case, with a view to building a solid defense.
Is DWI Similar To DUI?
The terms DWI and DUI are commonly used interchangeably. However, they’re not exactly similar, at least not in every jurisdiction.
DUI (Driving Under the Influence) is a general term for operating a motor vehicle while impaired by alcohol or drugs. It doesn’t define the level of impairment, making it difficult to use as a basis for establishing probable cause.
Is DWI A Misdemeanor or a Felony?
Driving while intoxicated is almost always a misdemeanor across the United States. San Antonio’s penal code classifies first DWI offenses as Class B misdemeanors.
However, certain circumstances may immediately elevate a DWI to a felony charge. Examples include the number and frequency of prior offenses, DWI with a minor passenger, the level of blood alcohol content, and DWIs that cause grievous bodily injuries or fatalities.
If convicted, penalties can range from probationary license suspension to hefty fines and a lengthy jail term.

What Are Field Sobriety Tests?
Field sobriety tests (FSTs) are standardized physical and mental exercises designed to enable law enforcement officers to assess if a driver is under the influence of alcohol or impairing drugs.
FSTs provide traffic cops with the most reliable way to evaluate a driver’s physical and mental capacity to operate a motor vehicle. Failing the tests will most certainly lead to an arrest.
Below are crucial things to know about field sobriety tests;
FSTs Come In Many Forms
There are multiple field sobriety tests a law enforcement officer may administer, including;
1. Horizontal Gaze Nystagmus (HGN)
The Horizontal Gaze Nystagmus Test involves getting a driver to track an object with their eyes. It’s designed to evaluate eye movement reactions, whose efficiency diminishes with an increase in blood alcohol content.
Jerking your eyes involuntarily indicates significant alcohol or drug impairment.
2. Walk-and-Turn
In the Walk-and-Turn Test, a traffic cop will ask you to take a series of steps in a straight line. You must walk heel-to-toe and turn on one foot, then walk back in precisely a similar manner.
The Walk-and-Turn Test checks for incoordination and your ability to multitask.
3. One-Leg Stand
This is perhaps the most dreaded of all field sobriety tests.
It involves standing with one foot off the ground and counting out aloud as a traffic officer checks for signs of imbalance like swaying and hopping.
4. Breathalyzer Test
While the first three tests require active physical participation, a breathalyzer (portmanteau for breath analyzer) test can be administered right from within your vehicle.
A traffic cop will have you blow into a breathalyzer, as the tool analyzes the alcohol content in your vapor almost immediately. Blood alcohol content in excess of 0.08% constitutes a DWI offense.

FSTs Aren’t Foolproof
The Texas District & County Attorneys Association reviewed previous studies investigating the accuracy of FSTs and found that these assessments can be up to 93% accurate. Regarding individual scoring, the Horizontal Gaze Nystagmus tops the practical tests. The Walk-and-Turn and the One-Leg Stand follow in that order.
Breathalyzer tests have been investigated independently, with studies pointing to an error margin of 15%.
However, multiple findings have challenged the credibility of field sobriety tests, with some studies indicating that these assessments can be less than 70% accurate. Therefore, failing the tests may not be sufficient evidence for a DWI conviction.
FSTs Aren’t Mandatory
In San Antonio, Texas, the law bars traffic officers from conducting mandatory field sobriety tests. You have a legal right to decline the tests, and that decision may not be used against you.
That said, traffic cops may still rely on other pieces of evidence to establish probable cause for arrest. Examples include:
- Apparent signs of intoxication, such as slurred speech and bloodshot eyes
- Physical evidence, such as a partially empty beer can
- Witness statements from passengers
FST Results Aren’t Always Admissible In Court
Field sobriety tests are legally admissible only if they were properly conducted.
An experienced San Antonio DWI lawyer can help establish whether FSTs were performed by a trained and certified law enforcement officer. They’ll also determine if due legal procedures were followed before your arrest.
For instance, the arresting officer must inform you that you’re under arrest before handcuffing you. They should also administer your Miranda rights and secure your vehicle and any occupants.
Even if due process was followed, your DWI attorney can still play a critical role in negotiating a plea bargain.

Final Thoughts
Understanding your rights in field sobriety tests is critical, as law enforcement officers rely on these assessments to establish probable cause for DWI arrests.
Remember that field sobriety tests are optional, and you can politely decline them without necessarily incurring automatic penalties. If you were coerced into taking a field sobriety test or you inadvertently agreed to the assessments, your best bet is to contact a DWI lawyer immediately.
Your San Antonio DWI attorney will represent your interests during the DWI proceedings and ensure you receive the best outcome possible. They’ll challenge the evidence, debunk the prosecution’s theory, and (if necessary) negotiate a favorable plea bargain.