How Do Officers Decide If Someone Fails a Field Sobriety Test?

Understanding What Really Happens on the Side of the Road and Why You Need a Private Attorney by Your Side

When someone gets pulled over and asked to step out of the car during a DUI stop, that's usually when the fear sets in. The officer says they want to check if you're okay with driving. They ask you to perform a few simple tests. You try to follow directions, even if you're tired or anxious. What many people don't realize is that field sobriety tests aren't as simple or straightforward as they sound. They're based on the officer's judgment — and that judgment can be flawed.

As a criminal defense lawyer who has handled countless DUI cases, I've seen how these tests are used in court. I've seen how officers interpret movements, posture, eye movement, and balance. What most people think of as "just cooperating" can quickly turn into evidence against them — and that's often based on very subjective decisions made in a matter of minutes.

Let me walk you through how these tests work, how officers decide whether someone has failed, and why hiring a private attorney right away can give you a real chance at challenging the entire stop.

The Three Standardized Field Sobriety Tests

There are three main field sobriety tests used by officers across the country: the horizontal gaze nystagmus, the walk-and-turn, and the one-leg stand. These tests were developed with the goal of helping officers assess whether someone might be impaired. But here's the problem — the scoring is based on things that aren't always obvious to the person being tested.

The Horizontal Gaze Nystagmus (HGN) Test

This test checks for involuntary jerking in your eyes. The officer holds a small object, usually a pen or finger, and asks you to follow it with your eyes. They're looking for eye movement that could suggest impairment. Most people have no idea what the officer is seeing or looking for. You just try to follow instructions, and they quietly make mental notes — often writing later that you "showed all clues of impairment."

The Walk-and-Turn Test

This is the one where you take nine heel-to-toe steps along a straight line, turn, and take nine steps back. The officer is watching for specific "clues" — like stepping off the line, using your arms for balance, not touching heel to toe, or turning incorrectly. They also count how many clues you show. Two or more can mean you "failed" in their view, even if you didn't stumble or fall.

The One-Leg Stand Test

In this test, you're asked to lift one foot six inches off the ground and count out loud until told to stop. You're being judged on whether you sway, hop, use your arms for balance, or put your foot down too early. Again, two or more clues may be used to suggest impairment.

What's important to understand is this: these tests aren't pass/fail in the traditional sense. Officers are trained to mark small movements or missteps as indicators of impairment. But those indicators aren't always linked to alcohol or drug use.

The Role of Officer Subjectivity

All three tests rely on the officer's interpretation. That means the officer decides if you moved your eyes the wrong way, stepped slightly off the line, or swayed just enough to be suspicious. The tests give officers a structure, but they still leave a lot of room for personal judgment.

I've handled many cases where the officer's report described my client as failing badly — but when I watched the bodycam footage, what I saw told a different story. In some cases, the person looked tired, maybe nervous, but certainly not impaired. But once the officer decides someone has "failed," that becomes the justification for the arrest, and everything that follows — the breath test, the booking, the report — is built on that moment.

That's why hiring a private attorney matters. I know how to review the details that others miss. I compare the officer's notes with the video. I check the lighting, the road conditions, what you were wearing, how long the test lasted, and how clear the instructions were. Many times, the officer's decision to arrest falls apart under that kind of review.

Other Factors That Affect the Tests

What a lot of people don't know is how easily outside factors can affect your performance on these tests. For example:

• Footwear – If you're wearing sandals, boots, or heels, walking heel-to-toe becomes harder.
• Road conditions – Uneven pavement, gravel shoulders, or sloped roads make balance harder to maintain.
• Weather – Rain, wind, or cold temperatures can throw off your coordination.
• Medical conditions – Back pain, knee injuries, vertigo, or inner ear issues can mimic signs of impairment.
• Age and weight – These tests weren't designed for everyone. They assume a certain physical baseline that many people don't meet.

These are the things I dig into when building a defense. If you had a condition or were in an environment that affected your ability to perform the tests, I'll raise that with the court. The officer may have treated the test like a simple checklist, but we show why that approach doesn't hold up.

Training and Instruction Matter

Officers are trained to give these tests in a very specific way. They're supposed to give clear, standardized instructions and demonstrate each test before asking you to perform it. But in many cases, they rush through the explanation, skip parts, or fail to demonstrate at all.

If the officer didn't explain the test clearly or gave mixed signals, that affects the reliability of your performance. I look closely at how the officer interacted with you — not just what the test was, but how it was administered. These small details can make the difference between conviction and dismissal.

Why a Private Attorney Can Make a Big Difference

If you've been arrested for DUI based on field sobriety tests, it's not the end of the road. These tests can be challenged. They're not scientific proof. They're observational tools, and they're often wrong. But to show that in court, you need someone who knows how to investigate them thoroughly.

When I take on a case, I get every piece of evidence — bodycam video, dashcam, police reports, officer training records. I look for timing, procedures, mistakes, and inconsistencies. I don't assume the officer got it right. I treat their interpretation like it needs to be tested because it does.

A private attorney has the time and focus to dig deep into your case. Public defenders often have huge caseloads and may not be able to spend hours reviewing bodycam footage or researching medical documentation that could help you. But when I work with you privately, your case gets my full attention from the start.

Field Sobriety Test Frequently Asked Questions

What does it mean when an officer says I "failed" the field sobriety test?

That usually means the officer saw two or more clues on the test — like stepping off the line or swaying during the one-leg stand. But those clues are based on the officer's interpretation, and they don't always mean you were impaired. Many factors can affect how you perform on these tests, including medical issues and nervousness.

Can someone be arrested based only on field sobriety test results?

Yes, but that doesn't mean the arrest is always justified. Officers can arrest you if they believe they have probable cause, and the field sobriety tests are often the deciding factor. A lawyer can review whether the arrest was legal based on the full context.

Do officers always follow proper procedures when giving these tests?

Not always. Officers sometimes skip steps, give unclear instructions, or fail to demonstrate the test properly. These mistakes can impact your ability to perform and can be used in your defense if documented and challenged early.

What if I have a medical condition that makes it hard to balance?

That's an important factor. If you have a health condition that could affect your performance, your attorney can use that to question the reliability of the test results. We may also use medical records or professional testimony to support your case.

Is the officer required to tell me the tests are voluntary?

In many states, officers are not required to inform you that you can refuse field sobriety tests. That's one of the reasons people take them — they think they're mandatory. But in most states that use DUI laws, the tests are voluntary.

Can poor weather or lighting be a valid reason for poor test performance?

Yes. Rain, darkness, wind, or uneven surfaces can absolutely affect how someone performs. If those conditions existed during your stop, your lawyer can use them to question the fairness of the testing process.

Does the officer's bodycam usually record the test?

Most departments use bodycams and dashcams that record the stop, including the field sobriety tests. This footage can be vital in defending your case, and your attorney should request it immediately to preserve it.

Should I hire a private attorney even if I think I failed the test?

Yes. Many people assume their case is lost because they didn't perform well. But an experienced private attorney can often uncover issues with how the test was administered or challenge the officer's observations. A poor performance doesn't always mean you'll be convicted.

Contact Musca Law 24/7/365 at 1-888-484-5057 For Your FREE Consultation.

Musca Law, P.A. has a team of experienced criminal defense attorneys dedicated to defending people charged with a criminal or traffic offense. We are available 24/7/365 at 1-888-484-5057 for your FREE consultation.