The Field Sobriety Test

If an officer has reason to suspect that a person is driving under the influence of an intoxicating substance, the officer is permitted to detain that person for a reasonable amount of time in order to investigate.  There are a variety of circumstances that may cause an officer to reasonably suspect that a driver is intoxicated.  For example, an officer may witness a car being driven erratically and immediately suspect that the driver is intoxicated or may become suspicious during the course of a regular traffic stop.  In any case, the officer must establish “probable cause” before an arrest can be made.  That means showing that it is more likely than not that the driver is intoxicated, which is commonly done by administering a Field Sobriety Test.

Field Sobriety Tests

There are many different types of Field Sobriety Tests.  Police departments may allow officers to choose which tests to administer or they may have a policy dictating which tests must be used.  The National Highway Traffic Safety Administration created the Standardized Field Sobriety Test (“SFST”), which many police departments have adopted.  The SFST involves three popular tests:  the horizontal gaze nystagmus, the one leg stand, and the walk-and-turn test.

Horizontal Gaze Nystagmus Test

During the horizontal gaze nystagmus test, suspects are asked to follow an object, such as a pen, with their eyes while holding their head still.  The officer moves the object from the center of a suspect’s field of vision towards their each of their ears.  If the suspect’s eyes jerk as they track the object then they have nystagmus.  Although nystagmus may occur without intoxication, the consumption of alcohol has been shown to cause the condition, with greater consumption being associated with more obvious eye movement.

One Leg Stand

An officer administering the one leg stand test will instruct the suspect to lift one foot roughly six inches off the ground and count out loud until the officer tells them to put it back down.  Signs of intoxication include hopping, swaying, putting the foot down too early and using arms to maintain balance.

Walk-and-Turn

The walk-and-turn test requires a suspect to take nine heel-to-toe steps in a straight line before turning on one foot and repeating the test in the opposite direction.  Observable indicators of intoxication include difficulty balancing before and during the test, beginning the test too early, inability to stay on the line, failure to walk heel-to-toe, taking too many or too few steps, and not turning on one foot.

More Information

Questions regarding Field Sobriety Tests should be directed at a qualified attorney, who can explain which tests are used in a particular location, what happens when a person refuses to take a test, and what to do if you fail a test.