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Attorney John Barnes, Attorney Brandon D. Fersten, and Attorney Oscar Butler

Standardized Field Sobriety Tests In DUI Cases In Knoxville and East Tennessee

Remember, standardized field sobriety tests are a fully voluntary test. A police officer cannot force you to complete field sobriety tests. 

Admittedly, it is very likely the officers will use your refusal as a basis for believing you are impaired, but they will have less evidence to use against you to establish your impairment. Significantly, the Tennessee Supreme Court has held in a case called State v. Bell that even if you pass the field sobriety tests, you can still be arrested, taken to jail, the court may find probable cause, and a jury can still potentially convict you of DUI. Clearly, at that point, there is no benefit to you performing field sobriety tests

Additionally, officers are supposed to ask if you have any medical conditions that prevent you from completing the test. If you do have a medical condition that may impact your ability to perform, it is especially important that you do not complete those tests. Then, we will work on collecting medical records to show the prosecutor and potentially the judge and/or jury. Officer are trained that for these tests to be “standardized” it should be instructed, conducted, demonstrated and performed the same way every time or else the results may not be valid. Similarly, if the test was conducted in poor weather conditions, on a slanted road, you are 50 or more pounds overweight, or you are over 65 years old (potentially even 60 years old) the tests may not be “standardized” and therefore not valid.

There are three (3) standardized field sobriety tests that all officers across the United States are trained to instruct and conduct in the same manner every time for the test to be validated in determining impairment.

3 Standardized Tests

  1. Horizontal Gaze Nystagmus (HGN) or the “eye test”

Commonly known to individuals who get arrested for suspicion of DUI as the “eye test”, the horizontal gaze nystagmus (HGN) is generally not admissible in Tennessee except under very limited circumstances. Nystagmus is an involuntary oscillatory movement of the eyeballs that occurs when an individual is impaired. However, there are many issues with officers relying on nystagmus to determine impairment. For example, some individuals have a natural nystagmus regardless of impairment, night driving, aspirin, certain medical conditions or diet, among other reasons other than impairment for nystagmus. Additionally, officers routinely improperly administer the HGN test. This test, when conducted by the police officer properly, is supposed to be 88% accurate at determining impairment above .08% when there are four or more clues out of six possible clues.

This test is not admissible in Tennessee because it is considered scientific in nature that requires the test to be admitted into evidence by an expert witness to which most officers are not qualified.


  1. Walk and Turn (W&T)

An individual’s performance on this test may be affected by back, leg or inner ear problems in addition to age, weight and environmental factors. Officers look for 8 possible clues on this test:

  1. Failure to maintain balance while listening to instructions
  2. Starting too soon
  3. Stop while walking
  4. Fail to touch heel-to-toe
    1. You have 18 steps you must take and therefore 18 potential steps where you may miss heel-to-toe to exhibit a clue. Significantly, you can touch heel-to-toe on 17 out of 18 steps but it will still be counted of a clue of impairment. Of course, this sounds unfair, but that is where our lawyers make it clear to the jury that even if you technically exhibited the clue, you performed the test well and the results of the test do not establish impairment beyond a reasonable doubt on their own.
  5. Step off line
  6. Use arms for balance (more than six inches)
  7. Improper turn or
    1. Improper turn is probably the most common clue we see. Officers usually state “take a series of small steps” and they demonstrate but too many people forget what to do for the turn. In short, your lead foot must remain on the line while you take those small steps to turn, rather than spinning or pivoting.
  8. Incorrect number of steps.

Two or more clues exhibited are allegedly approximately 79% accurate at determining impairment. However, officers will count a clue of impairment even if you exhibit the clue once out of eighteen (18) potential steps.

  1. One Legged Stand (OLS)

The final standardized field sobriety test requires you to balance on one leg for thirty (30) seconds; although the officer will tell you to continue until he tells you to stop and will not inform you that it is 30 seconds. Once again, this test requires a reasonably dry, hard, level and non-slipper surface, and back, leg or inner ear problems may impact the validity of this test. Similarly, a person who is overweight by 50 pounds or more, or is over the age of 65 will likely not be able to perform this test.

The four potential clues of impairment include:

  1. Swaying while balancing;
  2. Using arms for balance
  3. Hopping; or
  4. Putting foot down too soon.

Exhibiting two (2) or more clues is determined to be approximately 83% accurate of impairment.

While exhibiting clues on these tests may be indicative of impairment, there are numerous reasons other than impairment for why you may not have performed the test without clues. Our attorneys will discuss some of those factors that may be relevant in your case.

Additionally, even if you technically exhibit clues and fail to perform satisfactorily, jurors in jury trials often will attempt to complete these tests in the deliberation room and realize how difficult they are to complete without any alcohol. As such, we are more concerned about how you look overall during these tests than whether you technically exhibit clues, especially considering studies proving the tests are not 100% accurate; meaning there is reasonable doubt regarding impairment even if you fail the tests. 

More information can be found on our blog. 

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