DUI Field Sobriety Tests

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DUI Field Sobriety Test in Las Vegas

Police officers in Nevada and most other states use DUI field sobriety tests (FST) to help determine if a driver is intoxicated. They are typically the first step taken to detect an individual’s level of intoxication.

FST results are not the most accurate indicator of a driver’s blood alcohol content (BAC) for various reasons. Generally, DUI field sobriety test results are not enough to convict a person of a DUI. However, they can potentially be used as evidence to help prove the prosecution’s case.

Field sobriety tests check a person’s physical and mental capabilities to see if they are impaired. If you fail the tests, a police officer may place you under arrest and request you to take a breath test or blood test to discover a more accurate picture of your BAC levels.

At The Vegas Lawyers, our lawyers and paralegals are compassionate, savvy, and experienced. We know what we’re doing and can help you receive the least amount of penalties possible when charged with a DUI. We handle DUI cases in Las Vegas, Henderson, North Las Vegas, Boulder City, Searchlight, Mesquite, Laughlin, Goodsprings, and Pahrump.

History of Field Sobriety Tests

Before police officers benefited from technology and medical advancements to determine a person’s BAC, they strictly used field sobriety tests. Police officers deployed various methods of testing. Some were effective, and others have been proven to not be effective at all.

In 1975, the National Highway Traffic Safety Administration (NHTSA) began researching the most accurate methods of determining a driver’s level of intoxication. They worked closely with the Southern California Research Institute to determine which tests worked best.

Researchers traveled throughout the country to observe officers administering DUI field sobriety tests in different jurisdictions. After thousands of observations and years of research, they determined that only three tests were accurate and reliable enough to detect an individual’s BAC above .10 percent.

Since then, they have continued their research efforts and determined that these three standardized field sobriety tests can also reliably determine if a person’s BAC is above .08.

What Are The Three Standardized Field Sobriety Tests? (SFST)

Starting in 1981, law enforcement agencies across the U.S. began using the Standardized Field Sobriety Tests (SFST) recommended by the NHTSA. Those tests were The Horizontal Gaze Nystagmus test (HGN), Walk-and-Turn test, and the One-Leg Stand test to determine who they should arrest for DUI.

These tests are utilized to divide a participant’s attention by forcing them to listen, follow directions, and complete a physical action. FST’s make it difficult, by design, for a person under the influence of alcohol to pass the test.   

Police officers closely observe suspects during the tests to watch for signs of impairment. If they determine a driver is impaired, they will typically place them under arrest and administer a breath or blood test to ascertain their BAC levels more accurately.

The Horizontal Gaze Nystagmus (HGN) Test

While the name sounds very scientific, it’s actually a simple test. The horizontal gaze nystagmus test is just a basic eye-test. It works by the police officer placing a penlight (or similar object) in front of the suspect and directing them to keep their eyes fixed on the item while the officer moves it side to side.

As the test is administered, the police officer observes the suspects pupils for involuntary jerking movements (also called “nystagmus”). If detected, it could be a sign of high BAC levels. Generally, law enforcement officers are instructed to look for the following clues:

  • Disrupted pursuit: In theory, a sober person’s eyes won’t jerk when following a penlight. If they do, it could be a sign of intoxication.
  • Distinct eye twitching at maximum deviation: During the HGN test, you may notice the officer holding the penlight very far on each side for at least four seconds. When the suspect’s eyes are at “maximum deviation,” the officer observes for involuntary jerking.
  • Eye Jerking before the pen is at 45 degrees: While the officer moves the penlight from side to side, they check for involuntary jerking before reaching the maximum deviation point.

Officers score each suspect based on the number of indicators of intoxication they exhibit. If more than three indications of intoxication are observed, the suspect fails the HGN test.

The Walk-and-Turn Test

The Walk-and-Turn test works precisely as it sounds. Officers instruct participants to walk nine steps forward in a straight line (heal-to-toe) back and forth. When suspects turn around to come back towards the officer, they must keep one foot on the ground as they pivot. Suspects must verbally count the number of steps they take as they walk.

In general, police officers observe participants to ensure they follow directions, reasonably maintain their balance, and coherently count their steps aloud. In all, they are looking for eight signs of intoxication. Suspects who exhibit more than two “clues” fail the walk-and-turn test.

The One-Leg Stand Test

The one-leg stand test is administered in two stages. They include giving oral instructions and observing the participant’s performance. When the officer gives verbal instructions, they also provide a demonstration to ensure suspects understand what is being asked of them.

After the suspect lets the officer know they understand the instructions, the test begins. It entails standing on one leg with one foot six inches off the ground at a parallel angle. Hands must remain at the side while the participant looks at the extended foot and counts aloud until directed to stop (i.e., one one-thousand, two one-thousand, etc.).

During the test, the Nevada law enforcement agent is looking for the following:

  • Swaying
  • Using arms to maintain balance
  • Placing the raised foot on the ground or having trouble holding it up
  • Hopping to stay upright

If a suspect exhibits more than two indicators, they fail the test.  

What is a Police Officer Looking For During an FST?

During DUI field sobriety tests, officers are looking for many clues to determine a person’s intoxication level. In addition to the indications mentioned above, police officers are also observing if a person’s speech is slurred, if they smell like alcohol, and if they have bloodshot/watery eyes.

What Happens After The Field Sobriety Test?

If you fail an FST, the police officer will typically request you to submit to a preliminary breath test (PBT). If you fail the preliminary breath test, the officer will place you under arrest.

Those suspected of DUI who pass field sobriety tests are typically released. However, the officer may write them a ticket or citation, depending on the circumstances of the stop.

It’s important to remember police officers can still arrest suspects who pass field sobriety tests and preliminary breath tests so long as they have probable cause to suspect a driver is under the influence of alcohol or drugs.

What Can I Expect If I’m Placed Under Arrest For DUI?

If you fail an FST and/or PBT, the police officer will arrest you. At that time, you must take an evidentiary DUI breath test or DUI blood test (you have a choice in most cases). If they suspect you of driving under the influence of drugs (DUID), you must take a blood test.

Refusal of an evidentiary blood or breath test can lead to severe penalties such as mandatory license suspension of 1 – 3-years. Also, police officers can forcefully draw your blood if you refuse to take an evidentiary test. Officers must obtain a warrant before a forcible draw.

Does Nevada Law Require Me to Take a Field Sobriety Test?

Due to “informed consent” laws in Nevada, you can’t refuse an evidentiary test. However, you do have the right to refuse a DUI field sobriety test. Some DUI lawyers recommend refusing to take the test since it will give the state less evidence to scrutinize when attempting to prove a DUI case against you.

However, it should be noted that police officers will likely place you under arrest if you refuse to take the test. FST tests are not typically given to suspects physically unable to complete them, suffering from an injury, or too intoxicated to participate in the tests safely.  If you have bad knees or physical issues affecting your walk/gait, you should make sure to tell that to the officer.   

How Accurate Are Field Sobriety Tests?

As you can guess, DUI field sobriety tests are not the most accurate methods of measuring a person’s level of intoxication. When administered independently, the accuracy of each test is as follows:

  • Horizontal Gaze Nystagmus  – 77%
  • Walk-and-Turn – 68%
  • One-Leg Stand – 65%

When all three tests are used in concert, they are accurate 82% of the time. While that is a relatively high accuracy rate, it still means that nearly two out of ten DUI field sobriety test results are inaccurate. For this reason, the FST is not a reliable method of determining a person’s BAC to base a DUI charge.

Non-Standardized Field Sobriety Tests

Standardized field sobriety tests have been proven to be the most accurate forms of field sobriety tests. However, some officers use other non-standardized tests to help build a DUI case against suspects. They can include:

  • Finger to Nose Test
  • Hand Pat Test
  • Rhomberg Balance Test
  • ABC test
  • Counting Numbers Backwards Test
  • Vertical Gaze Nystagmus

Non-standardized tests are not reliable or a reasonably accurate method of determining a driver’s level of intoxication. For these reasons, Nevada police officers rarely use them since a skilled Las Vegas DUI lawyer will likely seek to exclude the results.

How a DUI Attorney Can Defend Against FST Results

There are many potential defenses for failed DUI field sobriety tests. The most common defenses include:

  • Inaccuracy and unreliability of DUI field sobriety tests
  • The test was taken in a poor environment
  • The defendant’s physical condition rendered them unable to perform FST tasks successfully
  • Procedural errors made by police officers or lack of appropriate training to administer the test effectively

If your Nevada DUI attorney uncovers discrepancies or mistakes, it can give them leverage when negotiating dismissed or decreased charges.

If your case goes to trial, it can be challenging for the prosecution to use FST results to prove intoxication beyond a reasonable doubt. This is especially helpful for defendants whose test resulted in borderline BAC levels (i.e., .08 – .10 BAC) via evidentiary blood or breath tests.


Contact The Vegas Lawyers Today

If you’ve been arrested for DUI, you face serious penalties if convicted. Consequences can include mandatory jail time, fines, license suspension, and more. Representing yourself against an experienced prosecution team is a gamble, to say the least.

Our lawyers and paralegals at The Vegas Lawyers understand the seriousness of DUI charges and will work tirelessly to investigate your case, scrutinize DUI field sobriety tests, and challenge the results.

Whether you are a tourist or live in Las Vegas and surrounding areas, we’re here to help. We routinely handle DUI cases in Las Vegas, Henderson, North Las Vegas, Boulder City, Searchlight, Mesquite, Laughlin, Goodsprings, and Pahrump.

Don’t gamble with your future when you don’t have to. Contact The Vegas Lawyers or give us a call today at (702) 707 – 7000 for your free initial consultation.

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