Nevada Field Sobriety Tests (FSTs): Laws, Accuracy, & Defense Strategies

If you are pulled over on suspicion of DUI in Nevada, the law enforcement officer will likely ask you to exit your vehicle and perform a series of physical and mental exercises known as field sobriety tests (FSTs).

You may lawfully refuse to perform DUI field sobriety tests in Las Vegas and throughout Nevada. However, officers will likely construe your refusal as probable cause for an arrest.

Three Standardized Field Sobriety Tests (FSTs)

1. Horizontal Gaze Nystagmus (HGN): Known as the “penlight test,” the HGN is where the officer looks for involuntary jerking of your eyes as they track a moving object.
2. Walk-and-Turn (WAT): This “divided attention test” is where you take nine heel-to-toe steps, pivot around, and take nine heel-to-toe steps back while counting the steps aloud.
3. One-Leg Stand (OLS): This “balance test” is where you count aloud for 30 seconds while standing on one foot while keeping the other about six inches off the ground.

Your Rights

• No “Implied Consent”: You are not required to perform field sobriety tests during a DUI investigation.
• Refusal Suggests Guilt: If you exercise your right to refuse the FSTs, the police will almost certainly use that against you when establishing probable cause.
• Other Tests are Mandatory: You are required to submit to a preliminary breath test administered roadside as well as the chemical breath test or blood test administered after a DUI arrest.

Defenses

• Incorrect Instructions: If police deviated from the instructions required by the National Highway Traffic Safety Administration (NHTSA), then any failing results could be invalidated.
• Incorrect Scoring: The police’s bodycam video may show that the officer incorrectly assigned you failing scores.
• External Factors: Sober people can fail FSTs due to poor weather, uneven pavement, unsupportive footwear, flashing police lights, medical conditions or injuries, old age, obesity, or fatigue.

While officers present FSTs as mandatory scientific tools, they are highly subjective and often administered incorrectly. Our Las Vegas DUI attorneys have a long track record of exposing the flaws in these tests to protect your driving record and your freedom.

Are Field Sobriety Tests Mandatory in Nevada?

No. Contrary to what an officer may imply at the scene, you have a right to refuse FSTs in Nevada.

• No Legal Penalty for Refusal: Unlike the preliminary breath test (PBT) or the evidentiary (“chemical”) blood or breath test, refusing an FST does not result in an automatic license revocation under Nevada’s “implied consent” laws.
• The Risk of Refusal: While you cannot be penalized for refusing, the officer will almost certainly use your refusal as “consciousness of guilt” to establish probable cause for an arrest.
• The Strategy: In most cases, it is advantageous for your case to politely decline FSTs. This prevents the prosecution from gaining subjective “evidence” of your impairment (such as swaying or failing to follow instructions).

Note that your FST scores are not just used by police to determine whether to arrest you for drunk driving (or drugged driving); they are also used by the court to determine whether to convict you. In the 2025 case Gonzales v. State, the Nevada Supreme Court concluded that the defendant’s FST results (among other evidence) was sufficient to uphold a DUI conviction even though circumstances rendered the blood-test evidence inadmissible.¹

The Three “Standardized” Tests (SFSTs)

The National Highway Traffic Safety Administration (NHTSA) has validated only three tests as “standardized.” If an officer deviates from the specific wording or conditions in the NHTSA SFST Student Manual, the results may be inadmissible in Nevada courts.²

1. Horizontal Gaze Nystagmus (HGN)

Commonly called the “penlight test” in Las Vegas, the HGN is where the officer looks for an involuntary jerking of the eye (nystagmus).

• The Clues: The officer looks for three clues in each eye (six total): (1) Lack of smooth pursuit, (2) Distinct nystagmus at maximum deviation, and (3) Onset of nystagmus prior to 45 degrees. Exhibiting four or more clues is failing.
• Accuracy: NHTSA claims 77% reliability, which is rather low.
• Defense: Nystagmus can be caused by over 40 medical conditions, including inner ear issues, caffeine, or certain prescription medications.

2. Walk-and-Turn (WAT)

In Las Vegas, the WAT is a “divided attention” test requiring you to multitask mentally and physically.

• The Clues: The officer looks for eight clues, such as starting before instructions are finished, losing balance during the turn, counting the steps aloud, or taking the wrong number of steps. Exhibiting two or more clues is failing.
• Accuracy: NHTSA claims 68% reliability, which is very low.
• Defense: This test is highly susceptible to “environmental” failures, such as passing traffic, uneven pavement, or wind.

3. One-Leg Stand (OLS)

In Las Vegas, the OLS is the test where you must stand on one leg and count aloud for 30 seconds.

• The Clues: The officer looks for four clues: (1) Sways while balancing, (2) Uses arms for balance, (3) Hopping, and (4) Puts foot down. Exhibiting two or more clues is failing.
• Accuracy: NHTSA claims 65% reliability, which makes the OLS the least reliable of all the SFSTs.
• Defense: Physical factors like being 50+ lbs overweight, back injuries, or being over age 65 can invalidate this test according to NHTSA’s own guidelines.³

Why FSTs Lead to False Positives

One out of four people who “fail” an FST is actually sober.⁴ In Nevada, we challenge results based on:

• Environmental factors, such as poor lighting, sirens/flashing lights, sloped or wet asphalt.
• Physical factors, such as inner ear infections, obesity, leg/back injuries, or fatigue.
• Officer errors, such as improper instructions, “clue” counting bias, or failing to ask about medical issues first.⁵
• Your attire, such as high heels (two-plus inches), tight clothing, or restrictive boots.

Non-Standardized Tests

Officers sometimes use “non-standardized” tests, which have zero scientific validation for determining BAC levels. These include:

• Rhomberg Stationary Balance: Standing with head back and eyes closed.
• Finger-to-Nose: Touching your nose with your eyes closed.
• Finger Count: Touching your thumb to each finger while counting.

In Nevada, we frequently file motions in limine to exclude these from trial because they lack the “scientific reliability” required under law. While these are often used in DUID (Drug Impairment) cases, they fail the “General Acceptance” test in the scientific community.⁶

How We Fight Your FST Results

Our Las Vegas DUI attorneys utilize a multi-pronged defense strategy:

1. Motion to Suppress: If the officer lacked reasonable suspicion to stop you or probable cause to arrest you, we move to have all FST evidence thrown out.
2. Cross-Examination of the Manual: We compare the officer’s body-cam footage against the NHTSA Student Manual. If they missed a single instructional step, the “standardization” is broken.⁷
3. Medical Experts: We use medical experts to testify that your “nystagmus” or “lack of balance” was due to a pre-existing condition, not alcohol.

In practice, some of the strongest FST defenses become apparent only after we compare the police report to the body-camera footage.

An officer’s report may reduce several minutes of roadside testing to statements like “lost balance,” “missed heel-to-toe,” or “used arms for balance.” However, the video may show that the pavement was sloped, the instructions were unclear, the officer demonstrated the test differently than instructed, or the driver actually performed much better than the report suggests.

We review the encounter step by step—not just the officer’s final conclusions—to determine whether each alleged sign of impairment has an innocent explanation and whether the tests were administered and scored properly.

Frequently Asked Questions

Can I record the FSTs on my phone?

Yes, you generally have a First Amendment right to record police officers performing their duties in public. However, do not physically interfere with the investigation or refuse lawful commands just to keep recording. Nevada law makes it a crime to willfully resist, delay, or obstruct a public officer performing a legal duty.

From a defense perspective, a recording can be extremely valuable. We have seen DUI reports make a roadside encounter sound much worse than it actually looks on video. An officer may write that a driver was “swaying,” “confused,” or unable to follow instructions, while the video shows someone standing normally, speaking clearly, and responding appropriately.

Your recording may also capture things the police report leaves out: confusing instructions, an improper demonstration, uneven pavement, traffic rushing past you, flashing emergency lights, wind, poor lighting, or an officer repeatedly interrupting you. If you recorded any portion of a DUI investigation, preserve the original video and give it to your attorney. Do not edit it or post clips on social media.

What if I passed the FSTs but was still arrested?

Doing well on the field sobriety tests does not guarantee that an officer will let you go. FSTs are only one part of the officer’s investigation. An officer may rely on other observations—such as driving behavior, the odor of alcohol, bloodshot or watery eyes, statements about drinking, or other circumstances—to decide there is probable cause for an arrest.

But good performance can become very useful evidence for the defense. When we review the body-camera footage, we are not limited to the officer’s conclusion that you “showed signs of impairment.” We can look at what you actually did. Were you steady on your feet? Did you understand complicated instructions the first time? Did you count correctly? Did you maintain your balance? Were you communicating normally with the officer?

Sometimes the most important evidence is the contrast between the report and the video. If an officer describes significant impairment but the footage shows a driver calmly following instructions and performing the exercises well, we can use that inconsistency to challenge the officer’s observations and, when the facts support it, the probable cause for the DUI arrest.

Does a bad back help my case?

It can. A bad back—or problems involving your knees, hips, ankles, legs, balance, or mobility—can provide an innocent explanation for difficulties on the Walk-and-Turn or One-Leg Stand.

This comes up frequently because those two tests require movements that have little to do with ordinary driving. Someone may be perfectly capable of safely operating a vehicle but have difficulty standing on one leg for 30 seconds or taking heel-to-toe steps because of an old injury, arthritis, surgery, chronic pain, limited range of motion, or another physical condition.

When we defend these cases, we look beyond the officer’s statement that you “failed” the test. Did you tell the officer about your bad back before starting? Did the officer ask about injuries or physical limitations? Is that conversation captured on body camera? Did the officer acknowledge your condition and then count the resulting balance problems against you anyway?

Medical records can also become important. If your records show that the back, knee, hip, or other physical problem existed before the DUI arrest, that can help establish that your difficulty with a balance exercise was not suddenly caused by alcohol. Even without medical records, body-camera footage showing an obvious limitation—or showing you telling the officer about it before the test—can give us evidence to challenge the officer’s interpretation of your performance.

Where did field sobriety tests come from?

Field sobriety tests were not always standardized. For years, police officers used a variety of roadside exercises, which could include counting backward, reciting portions of the alphabet, touching a finger to the nose, and other coordination tests.

Beginning in the 1970s, the National Highway Traffic Safety Administration (NHTSA) sponsored research through the Southern California Research Institute to determine which roadside tests were most useful for detecting alcohol impairment. Researchers initially considered six commonly used tests. Ultimately, NHTSA settled on the three-test battery still used today: the Horizontal Gaze Nystagmus, Walk-and-Turn, and One-Leg Stand tests.

The key word, however, is standardized. NHTSA’s conclusions depend on officers administering and scoring these tests according to prescribed procedures. When an officer changes the instructions, skips steps, conducts the test under inappropriate conditions, or scores behavior that is not actually a recognized clue, we can attack the reliability of the resulting FST evidence.

How is the walk-and-turn supposed to be administered?

The Walk-and-Turn involves much more than simply asking someone to “walk a straight line.” The officer is supposed to give specific instructions and demonstrate portions of the exercise before the test begins.

The driver is instructed to place one foot directly in front of the other, listen while the remaining instructions are given, and then take nine heel-to-toe steps along a designated straight line. After the ninth step, the driver must turn as instructed and take nine heel-to-toe steps back. The person is also instructed to watch their feet, count the steps aloud, keep their arms at their sides, and not stop walking once the test begins.

These details matter in a DUI case. For example, an officer should not simply tell a driver to walk along an imaginary path and then treat ordinary deviations as evidence of intoxication. We can review the officer’s instructions, demonstrations, body-camera footage, police report, and testing location to determine whether the Walk-and-Turn was actually administered under standardized conditions.

What does the walk-and-turn test measure?

The walk-and-turn is considered a “divided attention” exercise. In other words, police are not looking only at whether you can physically walk heel-to-toe. They are simultaneously judging whether you can remember and follow a series of instructions while performing the physical task.

That creates additional opportunities for innocent mistakes to be interpreted as impairment. A sober person who misunderstands an instruction, starts too soon, forgets to count aloud, or performs the turn differently from the officer’s demonstration can accumulate supposed “clues” even if their balance and coordination are otherwise normal.

This is one reason we look closely at exactly what the officer said before the test. A driver should not be blamed for failing to follow an instruction that was confusing, incomplete, demonstrated incorrectly, or never given in the first place.

How is the one-leg stand supposed to be administered?

The one-leg stand also has a specific procedure. The officer generally instructs the driver to stand with their feet together and arms at their sides until told to begin. The driver is then told to raise either foot approximately six inches off the ground, keep both legs straight, keep the raised foot roughly parallel to the ground, look at the elevated foot, and count aloud using the “one thousand one, one thousand two, one thousand three” method until told to stop.

The officer is supposed to time the exercise for 30 seconds. If the person puts their foot down during the test, NHTSA training materials instruct the officer to have the person raise it again and continue counting rather than automatically treating the exercise as over.

These procedural details can become important evidence. An officer who lets the test run too long, gives incomplete instructions, fails to demonstrate it properly, or scores conduct outside the recognized clues may make an already subjective test even less reliable.

How do roadside conditions affect FSTs?

The physical environment matters because the walk-and-turn and one-leg stand are balance exercises. Performing them on the side of a Las Vegas roadway at night is very different from performing them under controlled conditions.

We therefore examine where the officer conducted the tests and what the driver was dealing with at the time. A sloped, uneven, wet, loose, or slippery surface can affect balance. So can traffic, wind, poor lighting, distracting emergency lights, uncomfortable footwear, fatigue, age, weight, and physical problems involving the legs, back, or inner ear.

The important question is not simply whether the police report says you “failed.” It is whether the officer gave you a fair opportunity to perform a properly administered standardized test—and whether the supposed clues actually indicate alcohol impairment rather than the circumstances surrounding the test.

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