Field Sobriety Test

When an officer of the law stops a car it suspects is being driven by a person that could very well be driving under the influence of alcohol or marijuana, field sobriety and breathalyzer tests are administered to the driver to determine if he or she is actually impaired while driving and not weaving due to maybe texting while driving or having spilled a drink all over the car and having to clean it up. These tests are often a large portion of the state’s case against a driver that has been charged with a DUI and is now facing a trial to determine guilt and punishment.
A Field Sobriety Test (FST from now on) is the basic examination performed by the police officer or state trooper or whomever when they pull over a driver. The standards of the test were developed by the National Highway Traffic Safety Administration (NHTSA). The various sections of the test are the Horizontal Gaze Nystagmus, Nine Step Walk and Turn, and the One Leg Stand.

The Horizontal Gaze Nystagmus involves the officer shining a light into the suspect’s eyes and watching the motion of the eyes. When a person is impaired by alcohol, the nystagmus (the jerky movement of the eyes) is jerky. The drunker a person happens to be, the more magnified the jerkiness of the eye movement. If the person is not impaired, the movement of the eyes as they track left to right or right to left in a horizontal manner is smooth or less jerky. While police officers commonly use this test to determine impairment, there are other causes of an excessively jerky nystagmus. It is for this reason that failing this portion of the FST is not necessarily going to create a guilty conviction in trial but will often garner you an arrest.
The Nine Step Walk and Turn is the portion of the FST that we’ve all practiced to see if we can actually do it while sober. This test involves the officer dividing the suspect’s attention. He or she verbally explains how the test should be performed and also visually demonstrates. During the nine steps out, the turn, and the nine steps back, the officer watches for various signs of impairment such as loosing one’s balance. The suspect fails the test if he or she exhibits two of the eight signs impairment at once at any point during the test. It is meant to demonstrate with 68% reliability that the suspect is under the influence and has a BAC of .08 or higher.

The One Leg Stand is exactly what it sounds like. The officer asks the suspect to stand on one leg and not hop to maintain balance. The test has 4 easy areas to fail. If two of these 4 areas, such as hopping on one leg, are exhibited at the same time, the suspect is considered to have failed the test. This portion of the FST is also meant to de monstrate with 68% reliability that the suspect is under the influence and has a BAC of .08 or higher.

For more information regarding Field Sobriety Tests, contact Rhode Island DUI Lawyer James Powderly. As a lawyer certified in administering field sobriety tests, he’ll have all the information you could possibly want concerning FSTs

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James Powderly
Rhode Island DUI Attorney