If you're pulled over under suspicion of driving while intoxicated (DWI) in Galveston, Texas, there's a high chance you'll be asked to perform standardized field sobriety tests (SFSTs). These tests, widely used by law enforcement, were developed in the 1970s as a means to measure physical and cognitive impairment related to alcohol consumption. Although they were initially implemented in cities like Houston, these tests are now commonly used throughout Texas, including by Galveston County law enforcement.

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But how reliable are these tests? What do they actually measure, and how should you approach them if you're ever in a situation where you're asked to perform them? This guide breaks down everything you need to know about the three main SFSTs: the Horizontal Gaze Nystagmus (HGN), the 9-Step Walk and Turn, and the One Leg Stand.

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What Does It Mean for a Field Sobriety Test to Be "Standardized"?

The word "standardized" refers to the fact that these tests were rigorously studied by government researchers to determine their correlation with intoxication. This occurred in the 1970s when various motor skills tests were conducted on individuals with known blood alcohol levels. The goal was to link poor performance on these tests with higher levels of impairment. The research resulted in the adoption of three tests, which were deemed to provide officers with observable “clues” of intoxication. These clues allow law enforcement to form an opinion about whether or not a person is intoxicated.  You can learn more about this by reading the full NHTSA Manual available here. 

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When you're asked to perform these tests, understand that they're not designed to be "passed" in the conventional sense. The officer is merely looking for signs—often subtle—that can suggest impairment. These clues could include anything from swaying slightly during a balance test to showing involuntary eye movement.

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Horizontal Gaze Nystagmus (HGN)

The Horizontal Gaze Nystagmus, commonly known as the HGN test, is usually the first test administered during a DWI stop. The officer will hold a small object—like a pen or their finger—approximately 12 to 15 inches from your nose and slightly elevated. You’ll be instructed to follow the object with just your eyes, keeping your head still. The officer is observing for involuntary jerking movements in your eyes, a condition known as nystagmus.

The idea behind this test is that alcohol impairs the fine motor control of the eye muscles before affecting other larger muscles. This means that even in the early stages of intoxication, your eyes may exhibit subtle signs of impairment. The officer will specifically be looking for six clues, three in each eye:

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1. Lack of smooth pursuit: Your eyes should follow the object smoothly; if they don't, that’s a clue.

2. Distinct and sustained nystagmus at maximum deviation: When you look all the way to one side (maximum deviation), your eyes should remain steady. Jerking here is a clue.

3. Onset of nystagmus prior to 45 degrees: If the officer detects nystagmus before your eye reaches a 45-degree angle from your nose, that’s the third clue.

 

According to officers, if all six clues are present (three in each eye), they consider this a strong indication of intoxication. However, it’s worth noting that numerous factors besides alcohol can cause nystagmus, including certain medications, fatigue, and even eye conditions like optokinetic nystagmus (caused by tracking rapidly moving objects). As a result, the HGN test is often the most criticized and difficult to verify, especially without medical expertise.

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9-Step Walk and Turn

Next, you may be asked to perform the 9-Step Walk and Turn, a divided attention test that assesses both physical coordination and cognitive focus. This test requires you to place your left foot on a line (real or imaginary), then place your right foot in front of your left, heel-to-toe. You’ll have to remain in this awkward position as the officer provides the instructions.

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You will then be asked to walk nine heel-to-toe steps along the line, turn around using a series of small steps, and walk nine steps back. During this process, the officer will be observing for the following eight clues of intoxication:

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1. Losing balance during instructions: You’re required to stay in the heel-to-toe position while listening. Moving out of position counts as a clue.

2. Starting too early: If you start walking before the officer finishes giving instructions, that’s another clue.

3. Stopping while walking: Any pause or stop during the walk counts against you.

4. Missing heel-to-toe: Every step must be heel-to-toe; failing to touch even once is a clue.

5. Stepping off the line: If you lose your balance and step off the line, that’s another clue.

6. Improper turn: Not turning as instructed counts as a clue.

7. Using arms for balance: You must keep your arms by your sides throughout the test.

8. Taking the wrong number of steps: If you take more or fewer than nine steps, this also counts against you.

 

If the officer sees two or more clues, they are likely to classify you as impaired. It’s important to note that the test’s design inherently makes it difficult for most people to perform perfectly, especially in a stressful situation like a roadside stop. Minor mistakes, even those unrelated to intoxication, can quickly add up.

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One Leg Stand

The final standardized test is the One Leg Stand. This test is relatively simple in concept but can be surprisingly difficult in execution. The officer will ask you to lift one foot (your choice) approximately six inches off the ground, point your toe, and count aloud in a specific pattern (“1001, 1002, 1003…”). You must keep your arms at your sides throughout the test, which lasts for about 30 seconds. The officer will be looking for four specific clues:

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1. Swaying while balancing: If you struggle to maintain balance and sway, that’s a clue.

2. Putting your foot down: Lowering your foot prematurely counts as another clue.

3. Using arms for balance: You’re not allowed to use your arms to stabilize yourself.

4. Hopping: If you hop to maintain balance, this counts as a clue of intoxication.

 

Most people, regardless of intoxication, find this test challenging, especially in high-pressure scenarios. Even athletes and those with excellent balance often use their arms for stabilization, which can quickly lead to failure if the officer observes two or more clues.

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What Should You Do if Asked to Perform Field Sobriety Tests?

Deciding whether or not to participate in field sobriety tests is a complicated and personal decision. On one hand, refusing the tests provides the officer with less evidence to use against you. On the other hand, refusal almost always leads to arrest. Additionally, while field sobriety tests are not mandatory under Texas law, refusing them may prompt the officer to seek a warrant for a blood test.

If you do choose to participate, understand that these tests are designed to detect clues of intoxication, not to determine guilt or innocence. Even if you perform relatively well, the officer might still claim that you exhibited enough clues to warrant an arrest. Ultimately, whether or not to participate comes down to the circumstances of your case and how confident you feel about your ability to perform under pressure.

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How Can Galveston Criminal Defense and DWI Attorneys PLLC Help?

If you’ve been arrested for DWI in Galveston, it’s crucial to consult with an experienced DWI attorney. At Galveston Criminal Defense and DWI Attorneys PLLC, both Brian Foley and Luis Baez are former prosecutors who have specialized in handling DWI cases. With their experience and understanding of the complexities surrounding standardized field sobriety tests, they can craft a defense strategy tailored to the specifics of your case.

For more information on Galveston law enforcement and their DWI procedures, visit the Galveston Police Department.

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Whether you’ve been arrested after a DWI stop or are unsure about your rights during a roadside investigation, contact our firm today to get the representation you need.