Field sobriety tests were developed by the National Highway Traffic Safety Administration in the late 1970s. The idea was that individuals who were suspected of DUI should have to submit to standardized testing so that the investigation for DUI does not vary from jurisdiction to jurisdiction.

There are three standard field sobriety tests: the horizontal gaze nystagmus test, the walk and turn test, and the one-leg stand test. The tests must be administered according to the NHTSA guidelines. Otherwise, they are arguably invalid in court. A drunk driving lawyer could explain how Charleston DUI field sobriety tests work and how they may influence a case. Contact an accomplished DUI defense attorney today.

What is the Horizontal Gaze Nystagmus Test?

To conduct the horizontal nystagmus test, the arresting officer asks a driver to look at a stylus while moving it right to left and back and forth across a driver’s field of vision.  The officer is looking for involuntary jerking of the eyes, known as nystagmus. The presence of nystagmus during the test could mean the individual has consumed alcohol earlier in the night, but it is not a definite indicator of impairment.  There are dozens of other neurological conditions that can cause nystagmus.

Walk and Turn Test

The walk and turn test takes place a law enforcement officer asks a driver to take nine heel-to-toe steps down a straight line in one direction before turning around via a series of small steps and returning back to the starting point in the same way.  The NHTSA guidelines on field sobriety testing say a driver should be instructed to count their steps out loud, keep their arms down by their side during the test, look at their feet while walking the line, and to not stop until the test is completed.

One Leg Stand Test

The one-leg stand test is a standardized field sobriety test that requires an individual to lift one foot off the ground about six inches with the toe pointing forward and not up while the officer times the person for 30 seconds.  The person is supposed to count in a “one one-thousand, two one-thousand, three one-thousand,” etc. manner without using their arms for balance or putting their foot down until the officer tells them the 30 seconds is over.

How are Field Sobriety Tests Used at Trial?

The field sobriety test has no scientific basis for being admissible evidence in a DUI trial, but prosecutors in court often argue that they are the sole indicators of whether someone was under the influence. They will try to have a jury give greater weight to a driver’s performance on those tests than they likely deserve.  There is an inherently unreliable aspect of field sobriety tests that a defense attorney may need to explain to a jury to properly defend against any conclusions they are the most important indicators of impairment.

A person is allowed to refuse a field sobriety test at any time during a traffic stop.  If they are tired, older, or have certain physical limitations, they should seriously consider declining the opportunity to take field sobriety tests, as there is the potential for a harmful false negative.

How a Lawyer Could Help Handle a Charleston DUI Field Sobriety Test

If you have been arrested for a DUI following a field sobriety test that allegedly indicated impairment, it may be beneficial to reach out to an attorney. Judges and juries often overweigh the results of Charleston DUI field sobriety tests at trial, and the penalties of a conviction may be severe. An attorney could work to counter evidence from field sobriety tests and preserve a defendant’s future.