A Simmons & Wagner DUI Defense Insight
When most people think of a DUI stop, they picture an officer asking them to step out of the car and perform a series of “tests.” These roadside exams—known as Field Sobriety Tests (FSTs)—are supposed to help police determine whether someone is impaired. But what many don’t realize is that these tests are far from scientific, often highly subjective, and can unfairly lead to DUI arrests for people who are completely sober.
At Simmons & Wagner, we defend clients every day who were arrested based on FST results—even when the tests were administered incorrectly, judged unfairly, or impossible to perform given their physical condition. This blog breaks down what FSTs really measure, why they’re unreliable, and how our attorneys expose their weaknesses in court.
The Three NHTSA-Standard Field Sobriety Tests
The National Highway Traffic Safety Administration (NHTSA) recommends three standardized tests for officers to use during DUI stops:
- Horizontal Gaze Nystagmus (HGN)
- Walk-and-Turn (WAT)
- One-Leg Stand (OLS)
While these are considered “standard,” they’re still prone to error and often misapplied.
1. Horizontal Gaze Nystagmus (HGN)
What Officers Look For:
The officer moves a small object (usually a penlight) side to side in front of your eyes, watching for an involuntary jerking movement called nystagmus. They’re looking for:
- Lack of smooth pursuit
- Eye jerking at maximum deviation
- Eye jerking before your eyes reach a 45-degree angle
NHTSA claims HGN is the most reliable of the three tests—but only when performed perfectly, which is rare.
Why HGN Is Misleading
- Dozens of medical conditions cause natural nystagmus, including vertigo, inner-ear issues, and certain neurological conditions.
- Fatigue, stress, and dehydration can also trigger eye movement irregularities.
- The test must be performed at exact distances, angles, and speeds—any deviation skews results.
- Police are not medically trained, yet they’re expected to diagnose eye behavior normally examined by specialists.
How Simmons & Wagner Challenges It
Our attorneys analyze:
- Whether the officer performed the test according to exact NHTSA standards
- Whether there were distractions (lights, traffic, weather) that interfered
- Whether a medical condition or natural eye movement explains the result
- Whether the officer exaggerated or misinterpreted the “clues”
We often find the test was conducted incorrectly—not surprising, given its complexity.
2. Walk-and-Turn (WAT)
What Officers Look For:
You’re asked to walk nine heel-to-toe steps in a straight line, pivot, and repeat. Officers look for eight “clues,” such as:
- Losing balance during instruction
- Starting early
- Stepping off the line
- Using arms for balance
- Making an incorrect turn
- Wrong number of steps
Why the Walk-and-Turn Is Misleading
This test assumes all participants have:
- Perfect balance
- Good coordination
- No foot, knee, or back issues
- Good vision
- Stable footwear
- Calm, controlled breathing
In reality, many sober people struggle with this test due to:
- Uneven surfaces
- Gravel, rain, or sloped pavement
- Nervousness or anxiety
- Age or weight considerations
- Tight clothing or dress shoes
- Distracting traffic or flashing lights
Even NHTSA acknowledges the test has a significant margin of error. This is especially true when officers don’t follow the exact protocol.
How Simmons & Wagner Challenges It
We look closely at:
- Lighting and road conditions
- Wind, weather, and pavement quality
- How closely the officer followed NHTSA instructions
- Whether you have physical limitations
- Whether you were interrupted or rushed
- Footwear and environmental distractions
It’s common for sober drivers—especially older adults—to show the same “clues” officers associate with intoxication.
3. One-Leg Stand (OLS)
What Officers Look For:
You’re instructed to raise one foot six inches off the ground and hold it for 30 seconds without swaying, hopping, or putting your foot down.
Why the One-Leg Stand Is Misleading
This test is extremely difficult even under ideal circumstances. Many sober adults cannot hold one foot up for 30 seconds without some movement.
Factors that cause sober people to “fail” include:
- Poor balance
- Being overweight
- Ankle, knee, or lower back pain
- Fatigue
- Age
- Nerves
- Sloped or unstable ground
- Boots, heels, or sandals
Even NHTSA acknowledges this test is the least reliable of the three.
How Simmons & Wagner Challenges It
We examine:
- Whether the officer timed the test correctly
- Whether the ground surface made the test impossible
- Any medical issues affecting balance
- Whether the officer cut the test short or misinterpreted movements
- Footwear and weather conditions
We often show the court that what the officer saw was normal human balance, not signs of impairment.
Why Many Sober People “Fail” Field Sobriety Tests
Across all three tests, the biggest issues are:
1. They rely on subjective officer interpretation.
No machines. No measurements. Just one person’s opinion.
2. They were created decades ago and have limited scientific backing.
3. They don’t account for age, health, weight, or physical condition.
4. They’re performed in stressful roadside environments.
5. Small mistakes count as “clues” of impairment—even when unrelated to alcohol.
Many drivers arrested for DUI later test far below the legal limit, or even 0.00 BAC, yet were told they “failed” field sobriety tests.
How Simmons & Wagner Uses FST Weaknesses to Build a Strong DUI Defense
We don’t simply accept the officer’s interpretation. We investigate every detail. Our strategies often include:
✔ Challenging whether the officer followed required NHTSA procedures
Even one deviation undermines reliability.
✔ Requesting bodycam footage to expose inconsistencies
What the officer claims doesn’t always match what happened.
✔ Demonstrating medical or physical conditions that mimic “impairment”
Back pain, flat feet, vertigo, anxiety, neuropathy, and more.
✔ Highlighting environmental and roadside factors
Darkness, weather, sloped pavement, headlights, sirens.
✔ Showing the inherent unreliability of the tests
Especially HGN and OLS, which require near-perfect conditions.
✔ Using experts when necessary to counter officer testimony
Medical specialists and former police trainers can dismantle the prosecution’s narrative.
When these weaknesses are presented effectively, judges and prosecutors often question the validity of the arrest—leading to reductions, dismissals, or favorable negotiations.
If Field Sobriety Tests Led to Your DUI Arrest, Don’t Panic—Get Help Now
A “failed” field sobriety test does not mean you’re guilty. It doesn’t mean you were impaired. And it certainly doesn’t mean your case is hopeless.
Simmons & Wagner has helped countless clients challenge field sobriety tests and walk away with far better outcomes than they imagined possible. If you—or someone you care about—was arrested after performing these tests, you deserve a defense that knows how to dismantle them.
Contact Simmons & Wagner today for a confidential consultation.
We’re here to protect your rights, challenge unreliable evidence, and fight for the best possible result.