How Inaccurate are Field Sobriety Tests?

In the event of a traffic stop due to suspicion of DUI, many times, the police officer will ask the driver to step out of the vehicle and perform several tests, commonly known as field sobriety tests (FSTs). These tests are administered to determine a motorist’s level of intoxication prior to a breathalyzer test.

Field Sobriety Tests

The FSTs are used to asses one’s motor function skills at the most basic level. From doing various “line walks”, to hand-eye coordination tests, an FTS aims to emphasize one’s potential impairment. But because of the subjective nature of these test, they’re not always the most reliable measure.

The three most common FSTs include the following:

  • The walk-and-turn
  • The one-leg stand
  • The horizontal gaze nystagmus

More so, several studies have shown the inaccuracy of these tests. During the late 1970s, the National Highway Traffic Safety Administration (NHTSA) tasked the Southern California Research Institute (SCRI) with assessing multiple FSTs that were in use to determine which were the most accurate. SCRI sought the help of ten police officers for the experiment. They observed each subject perform various tests and determined which test participants had a BAC level of .10 percent or higher.

At the end of the study, SCRI recommended that the walk-and-turn, horizontal gaze nystagmus, and the one-leg stand be used to test for impairment. Unfortunately, when these tests were implemented in the real world, there was a 47% error rate among law enforcement.

In 1981, the NHTSA asked that SCRI conduct these tests again in order to reduce the error rate. Once again, the study produced mixed results.

The following are the results of the NHTSA-sponsored tests:

  • The accuracy rate of the one-leg stand is 65 percent
  • The accuracy rate of the walk-and-turn is 68 percent
  • The accuracy rate of the horizontal gaze nystagmus is 77 percent
  • The accuracy rate when all three were used together is 82 percent


There are various factors which can affect FST reliability. For instance, an officer who doesn’t follow all of the NHTSA guidelines when administering a test can miss key parts resulting in inaccuracies. Furthermore, some individuals may have specific health conditions that could affect their ability to perform these tests. Aliments such as a depth-perception vision impairment or a physical disability involving the motor function in one’s legs can easily sway one’s ability to successfully complete the test even if completely sober. Luckily, if you have any such impairment, not due to alcohol and are still legally able to drive, a simple breathalyzer test can clear up any potential suspicions.

Criminal defense lawyers often challenge FST results based on these types of errors. At Berry Law, we possess the comprehensive knowledge of Nebraska DUI law to help you navigate the complexities of your case and develop the most effective defense strategy possible to protect your rights.

If you have been arrested for a DUI in Nebraska, contact our experienced criminal defense attorneys at Berry Law today.

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