What Is a Field Sobriety Test?

Crime, DUI, Rights

field sobriety testField sobriety tests (FST) are a series of tests established by the National Highway Traffic Safety Administration (NHTSA) to help police officers determine when a driver is at or above the legal limit of .08 blood alcohol content during a DUI stop. You’ve seen it: people pulled over on the side of the road, attempting to show an officer that they can walk in a straight line, stand on one leg, or follow an officer’s pen with their eyes. While failure of these tests are good indicators of intoxication, they can be unreliable and lead to innocent people ending up with serious DUI charges. To avoid failing a field sobriety test, know what to expect from the test ahead of time and what an officer is looking for. Also, be prepared to arm yourself with evidence when an officer fails to do their job correctly.

Horizontal Gaze

A common FST is the Horizontal Gaze Nystagmus (HGN), otherwise known as the follow-the-finger test. In the HGN, an officer is not actually looking at whether you can follow his pen with your eyes; officers are looking for nystagmus, or eye jerking. A video of the test could show whether the test was performed properly–and whether your eyes were twitching or not, so this could be useful in court (or not, so show your lawyer the video first if possible). While your eyes will jerk if you are intoxicated, eye jerking can also be caused by diabetes or prescription drugs.

Walk and Turn

The Walk-And-Turn test is mostly known for its element of walking in a straight line; however, it’s a bit more involved than that. To challenge the test outcome in court — as with other field sobriety tests — you’ll need to prove that either the officer instructed you incorrectly or observed you incorrectly. While you may very well have walked in a straight line when asked by an officer, the WAT test actually looks for eight different clues: starting too soon, losing balance, stopping while walking, not touching heels to toes, stepping off the line, raising arms for balance (more than just 6 inches from your body), turning improperly or losing balance while turning, and taking the wrong number of steps. Fail just two of these, and you’ll fail the test.

One-Leg Stand

In the one-leg stand (OLS) test, you will be asked to stand on one leg and count for thirty seconds. Officers are watching for four clues: putting your foot down, raising arms for balance, swaying, and hopping. Do two or more of these and you’ll fail the test.

Preliminary Breath Test

You will likely be asked to provide a blood or breath sample if the officer suspects that you’ve been driving under the influence of alcohol. However, most officers will first ask you to blow into a preliminary alcohol screening (PAS) device to quickly determine in the field if you’ve been driving with a blood alcohol content above .08. You are not required to submit to a PAS test, but a refusal may lead to a one year license suspension.


  1. You have the right to refuse a FST. Your FST results are subject to a police officer’s competence and opinion in administering and observing the test, so it may be a risk not worth taking. Take more than one type of test if possible, if you suppose that could help rule out incorrect results from one test.
  2. Use your phone call — call a friend who could later testify that you were not slurring your speech and that you were in fact coherent. Better yet, leave a message on your own phone that could be played back later in court. Use your passengers as witnesses, especially if you do take an FST and their observations are different than the police officer’s.
  3. Evidence can help you if you were clearly not intoxicated and the police officer administered the test incorrectly, or if the officer lied on the report. Obtain video of the test, if possible. During a DUI stop, ask passengers to tape the officer’s instructions and you taking the test. This can be scrutinized later and used in court to prove an officer’s improper instruction or to show that you are obviously just clumsy and not drunk. If you have this evidence, an experienced DUI lawyer can then help find things to help you in court.
  4. A good DUI attorney can help identify mistakes and officer made during your DUI stop, which can help your case significantly.