How Accurate Are Field Sobriety Tests For Determining Whether A Driver Is Drunk?


One of the ways that law enforcement famously tests whether a driver is drunk is by putting the suspected drunk driver through a battery of roadside tests, commonly known as field sobriety testing. A driver could be pulled over as part of a traffic stop and be asked by law enforcement to participate in field sobriety testing, or a driver could be stopped at an Athens, Georgia sobriety checkpoint.

What Are Field Sobriety Tests?

You may have seen field sobriety tests on TV or in internet videos, but may not know exactly what is going on. Field sobriety testing is a battery of three psychophysical tests that are designed to test a driver’s reflexes and abilities. Based on how the driver performs these tests, law enforcement can make an educated guess as to whether the driver is intoxicated or not. Police officers must receive special field sobriety testing training, but a driver’s performance in these tests must be interpreted by the police officer, which means that the officer’s judgement plays a role in whether or not the driver will be arrested for DUI. When police judgement is a factor in any determination concerning a suspected driver’s state of intoxication, it means that there is plenty of room for the officer to make a mistake – either in observing the driver as the field sobriety tests are performed, or when making a judgement call about how the driver performs these tests.

There are three field sobriety tests: the one leg stand, the walk and turn test, and the horizontal gaze nystagmus (HGN) test. These tests were developed by the National Highway Traffic Safety Administration (NHTSA) as a nationwide standard for determining the likelihood that a suspected drunk driver is under the influence of alcohol to the degree that their ability to safely operate the vehicle has been compromised. Like any responsible government body, the NHTSA has engaged in research concerning the accuracy of the field sobriety tests. “Accuracy” correlates to when police officers correctly determine, based on the suspected drunk driver’s performance during field sobriety tests, that the driver is legally intoxicated, which corresponds to a blood alcohol concentration of 0.08 or higher.

  • One Leg Stand. This test requires that a driver stand on one leg, with the other leg bent at the knee so that the other foot is approximately six inches off the ground; the driver must then balance in this position for thirty seconds. During the NHTSA’s research, it was determined that police officers correctly identify intoxicated drivers about 83 percent of the time when using the one leg stand test.
  • Walk-and-Turn. To perform this test, a suspect must walk in a straight line nine paces heel-to-toe, turn about on one leg only, and return nine paces in a straight line. According to the NHTSA’s research, law enforcement correctly identify legally intoxicated drivers 79 percent of the time with the walk-and-turn test.
  • Horizontal Gaze Nystagmus. This eye test involves an officer observing the involuntary movements of a suspect’s eyes. The NHTSA has found that law enforcement can correctly identify a drunk driver by using the HGN test 88 percent of the time.

Overall, according to the NHTSA, law enforcement is about 90 percent accurate when using field sobriety tests to determine whether a driver is legally intoxicated. When you are facing DUI charges after participating in field sobriety tests, you need to reach out to an Athens field sobriety attorney that can help. Contact the Law Offices of J. Lee Webb if you are facing DUI charges in Athens. We can help you craft a personalized defense to your charges and fight for your rights throughout each step of your case.


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