Field sobriety tests are one way for the state to determine if a person charged with DUI was under the influence of alcohol or an intoxicant.

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Field sobriety tests (FSTs) are not the same as chemical or breath tests. Unlike chemical or breath tests, FSTs are not defined by law in Tennessee, where I practice. However, they can be a crucial part of a DUI case. FSTs are usually administered by the police officer who has stopped a driver suspected of DUI.

These tests include walking heel-to-toe in a straight line, touching the tip of the index finger to the tip of the nose, standing on one leg, holding your foot a certain distance from the car’s bumper, picking up coins from the ground, the horizontal and vertical nystagmus gaze tests, and reciting the alphabet.

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    Balance and Coordination Tests

    Two tests are used to determine balance and coordination – The walk and turn test, and the one-leg stand test. On both tests, the driver is scored based on the number of mistakes in performing the tests. For each mistake the driver is assessed one point. According to NHTSA, a score of two or more points on either of these tests indicates that the driver’s blood alcohol level is above .10 approximately 65% of the time.

    The Nystagmus Gaze Test

    Another common FST is the horizontal nystagmus gaze test. Nystagmus is the involuntary oscillatory movement of the eyeballs, and may be caused by intoxication. The purpose of the test is to observe the driver’s eyes for signs of intoxication.

    Under NHTSA guidelines, this test is administered by holding an object, usually a pen, 12-15 inches in front of the driver’s nose. The pen is moved from the center to the sides to determine if the driver’s eyes can follow the object smoothly, and also if the eyes can stay focused on the object without nystagmus (a rapid, jerky motion).

    So if you’ve been charged with a DUI in Memphis and took the field sobriety tests, what do you do now?

    If you have been charged with DUI after performing field sobriety tests, a DUI attorney should review the case in your defense. Field sobriety tests have become standardized through the work of the National Highway Traffic Safety Administration (NHTSA), which has evaluated the tests in both laboratory and field conditions to determine their validity.

    NHTSA requires that their testing and scoring procedures be followed exactly in determining whether the suspect is under the influence. Failure to do this could result in an invalid test.

    A Memphis DUI lawyer can review how these tests were administered and performed to look for invalid results.

    Failuring the walk and turn, or one-leg stand test, may be the result of nervousness, a medical disorder, or even the type of shoes worn by the driver or the surface of the ground. In other words, poor performance on the agility test may not necessarily mean an impaired ability to drive.

    For the nystagmus gaze test, there are strict federal guidelines that must be folowed when conducting the test. Therefore the way in which the test was administered should be carfully reviewed. For example, moving the pen too slowly or at the wrong distance may result in normal oscillation of the eyeball, which can be mistaken for nystagmus.

    Additionally, there are potentially dozens of non-alcoholic causes of nystagmus, ranging from medical to hereditary conditions, to diet. These issues can be investigated to possibly challenge the test results.

    Looking into the FSTs and their results are just one of many ways a Tennessee DUI case can be challenged.

    DUI defense also requires investigating into whether the police had probable cause to stop the driver, what the officer’s observations of the driver indicate in the police report, examining the chemical or breath test (if any), and evaluating whether the state can prove its case beyond a reasonable doubt.

    Patrick Stegall is a Memphis DUI lawyer. He represents individuals charged with DUI in Memphis, Germantown, Collierville, and Fayette and Tipton Counties. If you would like Mr. Stegall to review your DUI case, please call him at (901) 205-9894 or email at

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