When an officer suspects that a driver may be under the influence of alcohol or drugs, they can ask the driver to perform certain tests to determine intoxication. Known as field sobriety tests, these tests are intended to help an officer determine a suspect’s level of intoxication without a breath or blood test.

While there are a number of field sobriety tests that officers can use, only three have been scientifically validated and approved by The National Highway Traffic Safety Administration as reliable tools for judging a person’s BAC:

  • One leg stand
  • Walk and turn test
  • Horizontal Gaze Nystagmus (HGN)

Other common tests include reciting the alphabet backwards, touching your nose with your fingertip, and other complicated steps. As these tests are not as accurate and have been proven to be challenging for people that have no alcohol in their system, they are not used to provide definitive proof of DWI.


This is a commonly used test that requires a person to stand on one leg and count by thousands. During administration of the test, the officer is required to ask if the driver understands the instructions and make sure that they give acknowledgement.

During this time, the officer will look at whether or not the driver sways when trying to balance, uses their arms to stay balanced, is forced to hop around, and how many times they put their foot down during the test. Since this is a physical test, if the driver has any disability that prevents them from performing the test correctly, they can inform the officer.


Similar to the one leg stand test, this is a physical test, and may not be possible for those with certain disabilities or injuries. The test will include 9 heel-to-toe steps, then a turn, and 9 heel-to-toe steps back down the line. During the process, the suspect must keep their arms at their sides and stay on the line.

The officer will look at whether or not the driver stepped off the line, failed to take heel to toe steps, made an improper turn, and other factors. The officer must make sure the driver understands the test and confirms this before they are required to start.


In this test, an officer will check the driver’s eyes to determine if they are above the legal BAC limit. The officer will direct the suspected driver to keep their head still and to follow a small stimulus such as a pen or flashlight with their eyes only. As the officer moves the stimulus, the suspect will need to track it with their eyes only.

The officer will be looking to see if the suspect’s eyes bounce while following the stimulus. They will also look for distinct nystagmus, which is a sign of intoxication.

These three tests are just examples of the standardized tests that officers can use. If they use other options, it will be up to your lawyer to prove whether or not they were fair, reliable, or accurate.

If you were arrested for DWI after failing a field sobriety test in the Dallas area, contact our experienced defense lawyers at The Wilder Firm to learn how we can fight your charges!