Chapter 12: Standardized Field Sobriety Tests - Walk The Line, Stand On One Leg.. What These Tests Really Mean

When an officer investigates a suspected DUI, he will often have the person he is investigating perform certain tasks. Some of these tasks or tests are standardized and are used in many DUI stops and some are completely made up by individual departments or even individual officers.

We have heard of officers dropping coined change on the ground and asking a suspect to pick it up, as well as the infamous “say your ABCs backward” test. There are other non-standardized tests that are more prevalent including the finger-count test, the Rhomberg balance test, the finger to nose test, and the lack of convergence test. None of these tests are “standardized” and none have ever been conclusively shown to be able to predict impairment by the National Highway Traffic Safety Administration (NHTSA), the body that studied and standardized the 3 most often used field sobriety tests. It is important that your attorney challenges the validity of these non-standardized tests because the State will likely try to use them to prove that you were under the influence and because there is little evidence to support that claim for many of the non-standardized tests.

There are three “standardized” tests, for which the NHTSA has prescribed very specific training and administration. These tests are the Horizontal Gaze Nystagmus Test, the Nine Step Walk and Turn Tests, and the One Leg Stand Test. One thing to keep in mind for all of these tests, and that is the only all caps and all bold language in the entire NHTSA training manual is that “IF ANY ONE OF THE FIELD SOBRIETY TEST ELEMENTS IS CHANGED, THE VALIDITY IS COMPROMISED.” That statement is vitally important and true. The tests were designed to be given in a particular way to people who qualify to take the tests. If someone is more than 65 years old, more than 50 pounds overweight, or has particular back, leg, knee, or inner ear problems, the tests should not even be given because they are unlikely to yield accurate results.

There are a multitude of other factors that can affect the outcome of the tests that your lawyer will explore with you.

Horizontal Gaze Nystagmus Test

Many people tell me that they passed this test without actually knowing what the officer is looking for. The objective is not to see if someone can follow a light or pen with their eyes, but instead to determine whether “nystagmus” is present. Nystagmus is a rapid jerking of the eyes and can indicate alcohol intoxication. There are three clues in each eye an officer looks for: (1) “a lack of smooth pursuit” (jerking during eye movement; (2) “distinct and sustained nystagmus at maximum deviation,” (jerking when the eye is looking to the extreme left or right; and (3) “onset of nystagmus prior to 45 degrees.”

While alcohol intoxication can cause nystagmus, so can dozens of other conditions. Additionally, this is a very difficult test to correctly administer and score and should be performed by someone with a scientific or medical background. Our Tennessee appellate courts have held that the HGN test is a scientific test, and for that reason, it is almost never used in evidence at a DUI trial because it is a very rare officer who can qualify as a scientific expert on nystagmus. As such, if the State cannot provide an expert witness to discuss the HGN test in detail, the test will be inadmissible at trial and thus, the State is only left with 2 other field sobriety tests to use against you at trial.

Nine Step Walk-and-Turn

The walk and turn test requires the subject to walk in a straight line, touching heel to toe, without stepping off the line, missing heel to toe, raising arms for balance, walking nine steps, making a turn with a series of small steps and returning nine steps in the same fashion.

There are 8 possible clues that an officer is looking for and according to the original NHTSA study, 2 or more clues indicates a blood alcohol level over .10%. There are dozens of opportunities to exhibit a single clue on this test. For instance, missing heel to toe on just 1 out of the 18 steps equals one clue, the same is true for stepping off the line just once.

Even though this is a difficult test to pass, there are specific things that your attorney should look for. For instance, did the officer correctly instruct and demonstrate the test? If not, it would not be fair to count the test against you. Also, was the test performed on a flat, non-slippery surface and were heels or boots allowed to be removed? If not, the test may be invalid. Finally, was the person tested even a good candidate to take the test or would he or she fail whether intoxicated or not due to some medical condition. However, even when the test is instructed by the officer perfectly, this test is still not conclusive evidence of DUI.

The One Leg Stand

The one leg stand requires the person being tested to stand on either leg with their other leg extended out approximately six inches off the ground, with hands down by the person’s sides and with their toe pointed out.

There are four clues that officers are looking for on this test, including swaying, hoping, putting a foot down, and raising arms for balance. Any two of these clues, if present even once, indicates a blood alcohol concentration of .10% or greater according to the original NHTSA study.

Like the other tests, the one leg stand must be administered, instructed, scored, and demonstrated properly in order to be valid. Also, like the other tests, there are many circumstances that would make a person a poor candidate to take the one leg stand or that would cause them to demonstrate clues for reasons other than impairment. A good DUI lawyer will know what questions to ask and what to look for on the video of your tests to challenge the officer’s determination that the test indicated that someone was impaired by drugs or alcohol. Once again, this test is not conclusive evidence of DUI because many individuals that are not impaired cannot “pass” this test because of various conditions outlined above.