Walk the Line: Field Sobriety Testing

The National Highway and Traffic Safety Administrations (NHTSA) standardized field sobriety tests often form the basis for probable cause to arrest a person on suspicion of DUI. These tests, in theory, are supposed to evaluate an individual’s motor coordination skills.

The NHTSA has established three (3) standardized tests:
• Horizontal Gaze Nystagmus (HGN)
• Walk and Turn Test
• One leg stand test.

Nystagmus is the involuntary jerking of the eyes. This involuntary jerking and a lack of smooth pursuit (horizontal gaze) of a pencil or pen light can mean that a person is under the influence of alcohol or some drug. While involuntary jerking can demonstrate intoxication there are several medical explanations such as diseases of the inner ear, and other physical disorders which could also cause a person’s eyes to simulate that movement.

The Walk and Turn Test requires that the individual walk on a line either real or imaginary. The person’s left foot must move in a line ahead of his right foot in a “heal to toe” stance. The person is required to keep their arms at their sides and take (9) nine “heal to toe” steps, turn, and take 9 more “heal to toe” steps. This test also requires that the officer demonstrate the movements prior to asking the individual to complete it.

The One Leg Stand Test, similar to the Walk and Turn Test, requires that the officer provide the individual with instructions and provide a demonstration. This test requires a person to raise one foot approximately six inches off of the surface and keep it parallel to the ground. While holding that position the individual is required to count out loud until told to stop.

All of these tests obviously require some type of physical coordination and many individuals would have trouble completing them even if they had not ingested any alcohol. An effective and proper DUI defense attacks the proper administration of these tests. If one or more of these tests are not administered correctly, the prosecution may fail to establish probable cause during a Motion to Suppress. Remember that a DUI suppression motion focuses on the officer’s conduct prior to the arrest. This conduct or lack of proper conduct is often the best defense to a DUI charge.