Accuracy of Field Sobriety Tests

Field sobriety tests (FSTs) are commonly used by law enforcement to determine whether a driver is impaired. However, the accuracy of these tests can be challenged in court as a DUI defense strategy.

FSTs are not always reliable indicators of intoxication and can be affected by factors such as age, weight, physical condition, and even the weather. Additionally, officers may not administer the test correctly or accurately interpret the results. As such, it is important to understand that FSTs are not foolproof and can be successfully challenged in court. This article will highlight the types of FSTs (standardized and non-standardized/alternative) and the problems with those specific tests.

Are Field Sobriety Tests Accurate?

FSTs, even standardized tests, are not 100% accurate. According to data from the National Highway Traffic Safety Administration (NHTSA), the horizontal gaze nystagmus test is only 88% accurate. The one-leg stand is 83% accurate, and the walk-and-turn test is only 79% accurate. Later in the article, we will discuss factors that can affect the accuracy of the field sobriety test results.

Field Sobriety Tests Standard vs. Non-Standard

Field sobriety tests (FSTs) are used by police officers to determine if a driver is impaired. The NHTSA has sanctioned three field sobriety tests: the horizontal gaze nystagmus, the one-leg stand, and the walk-and-turn test. These are known as standardized field sobriety tests (SFSTs).

SFSTs are nationally recognized drills taught to all law enforcement officers capable of arresting someone for driving under the influence of alcohol or drugs. In addition to SFSTs, alternative field sobriety tests (AFSTs) exist.

AFSTs are not officially sanctioned by NHTSA, but may still be used by law enforcement officers in certain situations. Examples of AFSTs include counting backward, reciting the alphabet, and finger-to-nose testing. Unlike SFSTs, AFSTs do not have set criteria for determining impairment and therefore can be more subjective in nature.

Types of Field Sobriety Tests & Problems with Each Test

As we mentioned, there are three standard field sobriety tests that the NHTSA introduced and standardized in 1981, and states do not have to adhere to the federal standard and can allow their officers to conduct AFSTs. Here are more detailed descriptions of what each test can entail:

Horizontal Gaze Nystagmus.

The Horizontal Gaze Nystagmus (HGN) test, more familiarly known as the eye test, is one of law enforcement's common tools for suspect evaluation in cases where alcohol has been involved. By having a subject stand still and track an officer-held object with their gaze, the HGN test aims to detect impairing signs caused by intoxication. However, many medical or factual bases can render this field sobriety test inconclusive in court proceedings.

During the test, the officer will be trying to determine whether your eyes jerk from side to side or your eyes track the object smoothly. This test was initially created for medical professionals to see if patients had neurological disorders or injuries.

Due to risks associated with certain medical conditions (i.e. astigmatism, concussions, head injuries, etc.), officers are warned not to conduct field sobriety tests on individuals diagnosed with astigmatism or who suffered head trauma in the past. However, in many cases, they still conduct the test, document that the person claimed they had a condition, and try to factor in your medical condition during their evaluation.

The problem with continuing to administer the HGN test when the person has a condition is that officers are not medically trained professionals. They do not have the proper training or experience to consider the impact your injury or disorder will have on your eye movement/the test results.

Other problems with this test include:

  • Wind, flashing lights, and other environmental factors can affect the test interpretation and results
  • The test was created and validated in a controlled environment and did not factor in how a person’s mental or emotional state (after being pulled over) can affect the test.

One-Leg Stand

The one-leg stand test requests that you assume a stationary position where both feet are placed together and your hands remain at the side while an officer provides instructions. To demonstrate steadiness, you must lift either leg approximately 6 inches off the ground without bending it or swaying excessively. While lifting your leg, you will be asked to count out 30 seconds and look at a fixed point.

Officers are looking for signs that you struggled to follow their instructions. They will also look to see if you:

  • Drop your foot
  • Sway while standing
  • Raise your arms for better balance
  • Need to hop during the test

The problems with this FST include that:

  • The test was created to precisely measure alcohol levels above .10, not below.
  • The test, like all FSTs, was created and validated in a controlled environment without external distractions like passing vehicles or bad weather to ensure accuracy.
  • The test can be hard for specific groups of people to pass, specifically those with joint disorders, depth perception issues, leg or back injuries, or a history of head trauma/injuries.
  • The test can be hard for those over 30 years old to pass, as your ability to balance begins to decline at that age.
  • The test can be beaten/made easier if you stiffen your legs and buttocks while performing the test, and while law enforcement officers are taught this trick, the people pulled over on the side of the road are not.


This test involves you standing in a position that the officer asks you to stand in while they instruct you on the test. Once they believe you can perform the test and understand their instructions, you will be graded on your ability to adhere to their instructions and the walking phases.

To be more specific, you will be asked to walk heel to toe, in a straight line (usually on the white line), while keeping your hands directly at your side. Once you walk to a certain point, you will be asked to turn and walk back.

Officers are looking to see whether you have the ability to:

  • Complete the tests without walking off the line
  • Keep your hands by your side throughout the entire test
  • Stand with your hands by your sides while walking
  • Turn in the way the officer told you to turn
  • Walk about nine steps down the line and back while going heel-to-toe
  • Walk without stopping

Taking the walk-and-turn test can be an intimidating experience due to its strict requirements for participants. Under duress, walking in such close confines on a public roadway is challenging—not just physically but also mentally under threat of possible DUI arrest and jail time. This test can also be problematic as:

  • Anyone with back, leg, hip, or ankle issues can struggle to meet the test requirements.
  • Officers may arrest a suspect if they believe you do not have two of the aforementioned abilities.
  • This test's results may be unreliable if the administering officer does not follow all prescribed protocols.
  • The test’s result can also be affected if it is taken in any terrain other than a smooth and level surface or during inclement weather.

Counting Backward

A police officer may put drivers to the test by having them count backward from a certain number, whether it be 10, 100, or even 1000. The driver is tasked with recalling and reciting these numbers in reverse order until instructed otherwise.

Counting numbers backward is a divided attention test. During the exam, impaired motor skills or difficulty following instructions may be interpreted as signs of intoxication and cause for further evaluation. This task places cognitive pressure on drivers in order to detect any underlying impairment.

Even an innocent driver can be seen as impaired, due to officer error or inaccurate test results. Nervousness and fatigue are just a few of the many factors that may influence performance on field sobriety tests; subjectivity further complicates matters by leaving ample room for subjective interpretation.

Despite having been around for ages, this alcohol impairment test has yet to gain recognition from NHSTA as a standardized measurement of physical and mental incapacity. This puts it at an obvious disadvantage in legal proceedings when compared to other field sobriety tests accepted by courts nationwide.

Finger-to-Nose Test

The finger-to-nose test is a non-standardized method of gauging intoxication. With your eyes closed, the officer will observe as you tilt your head back and touch your nose with an index finger - repeating this action three times per hand for a total of six attempts. Officers will be trying to see if you demonstrate any potential signs of impairment due to alcohol or other substances, such as a(n):

  • Body tremors
  • Eyelid fluttering
  • Failing to touch your nose with your finger
  • Inability to follow directions
  • Speaking or making noises while taking the test
  • Swaying

As this test can be somewhat subjective, an officer’s perception can be skewed if they already believe you to be under the influence. Also, this test was initially developed to test a person’s motor coordination and neurological function in medical situations; similar to the HGN test, officers are not medical professionals and are likely unable to tell whether test failure is due to a medical condition.

Reciting the Alphabet

Many are under the misconception that they must recite the alphabet in reverse order (i.e. from Z to A) to pass the ABC test, but this is not so. In fact, you will typically only be asked to repeat partial sequences or even just one letter of the officer’s choosing, "d" through "r", for example. For more difficult cases, reciting all 26 letters may prove necessary.

During the test, officers will look to see if you are:

  • Slurring your speech
  • Struggling to follow directions or recall the next letter

The ABC test lacks consistent guidelines and is not one of the three standard field sobriety tests recognized by the NHTSA, making its results untrustworthy. Variations in administration from officer to officer make it difficult to compare or confirm accurate scores between different cases.

Also recalling your ABCs can be a challenge for various reasons. Language differences, nervousness, and educational level are all factors that could affect an individual’s ability to accurately recite the alphabet; even external influences like noise disruption may further impede their success on this test.

Can You Challenge the Results of Field Sobriety Tests in WV?

While field sobriety tests can be accurate in determining impairment, they are not infallible. It is possible to challenge the results of a field sobriety test if you believe that the results were inaccurate or that the test was administered improperly.

When challenging the results of a field sobriety test in West Virginia, it is important to understand how these tests work and what factors may affect their accuracy (with respect to the accused’s physical impairments and injuries, etc. as well as environmental factors). Law enforcement officers must follow specific procedures when administering field sobriety tests in order for them to be considered valid evidence in court.

If an officer fails to follow proper protocol when conducting a test, then this could be grounds for challenging its results. Additionally, if an officer does not provide adequate instructions or fails to properly observe and document the results of a test, then this could also be used as evidence against its validity in court.

Working with an experienced DUI attorney, they can work to investigate the circumstances of the field sobriety test. They can develop a personalized case strategy to help you get FTS results dismissed.

It is important to note that you do not have to take any FSTs if asked by an officer. Refusing an FST does not automatically mean that you will be arrested or charged with a DUI and West Virginians have the legal right to not perform the test. While the officer may still arrest you for a DUI, FST (or lack thereof) results cannot be used against you.

Trusted & Reliable DUI Defense Services

If you or a loved one have been arrested or charged with a DUI, you should consult with an attorney who specializes in criminal defense or even more specifically DUI defense cases. At The Wagner Law Firm, our attorney has over two decades of legal experience, and Attorney Wagner has successfully defended thousands of clients in a variety of DUI defense cases—including everything from misdemeanors to DUI homicide cases.

Learn more about how The Wagner Law Firm can help you by calling (304) 461-6000 or completing our online contact form.