How Accurate are Field Sobriety Tests?

In the event of a traffic stop due to suspicion of DWI, the police officer may 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.

The three most common FSTs include the following:

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

However, 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 were there to watch each subject perform various tests and to determine 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 percent error rate among law enforcement.

In 1981, the NHTSA decided 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 result in inaccuracies. Furthermore, some individuals may have specific health conditions that may affect their ability to perform these tests.

Criminal defense lawyers often challenge FST results based on these type of errors. At The Law Office of Rene A. Flores PLLC, we possess the comprehensive knowledge of Texas DWI law to help you navigate the complexities of your case and develop the most effective defense strategy possible to protect your rights and future.

If you have been arrested for a DWI in Texas, contact our Hidalgo County criminal defense attorneys at The Law Office of Rene A. Flores PLLC today.

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