Types of Standardized Field Sobriety Tests

Drinking and driving is a serious crime in Washington state. To keep other drivers and pedestrians safe on the road, police officers often perform standardized field sobriety tests during traffic stops. There are three types of standardized sobriety tests: horizontal gaze nystagmus, the walk-and-turn, and the one-leg stand.

#1: Horizontal Gaze Nystagmus

Alcohol can impair many body functions, including concentration, vision, and eye movement. Police officers administer the horizontal gaze nystagmus (HGN) test as a way to test a suspected offender’s eyes. Nystagmus is a term that refers to the bouncing or jerking of the eye, which often occurs when a person is looking at high peripheral angles. However, nystagmus occurs at a lower angle than normal when a person is drunk.

During a HGN test, a police officer will ask the driver to follow a slowly moving object with his or her eyes. The officer will look for a few key indicators of impairment during this test.

• The eye cannot follow the moving object smoothly.
• The nystagmus is distinct and sustained even when the eye is held at the peripheral angle or when the eye is held for more than four seconds.
• The nystagmus begins to occur before the eye reaches a 45-degree angle.

If the officer detects four or more clues between the two eyes, the driver is likely under the influence of alcohol.

#2: The Walk-and-Turn

Like eye movement, alcohol also impacts motor skills and coordination. It can be difficult for impaired drivers to walk upright or in a straight line—which the walk-and-turn test seeks to identify.

During the walk-and-turn test, the police officer will ask the driver to take nine steps along a straight line. The officer will instruct the driver to touch his or her heel to his or her toe while taking each step. When the driver reaches the end of the nine-step walk, the officer will ask him or her to turn on one foot and perform the test again in the opposite direction. While observing the driver, the officer will look for the following signs of impairment.

• The driver cannot keep his or her balance while listening to the instructions.
• The driver takes an incorrect number of steps.
• The driver makes an improper turn or movement.
• The driver cannot walk in a straight line.
• The driver stops to regain balance during the test.
• The driver does not touch his or her heel to his or her toe.
• The driver uses his or her arms to balance during the test.
• The driver begins the test before the officer finishes giving the instructions.

If a police officer identifies two or more of these indicators, the driver is likely under the influence of alcohol.

#3: The One-Leg Stand Test

The one-leg stand test is the third prong of a standardized field sobriety test. The police officer will instruct the driver to stand on one leg with one foot six inches off the ground. While standing, the driver will need to count aloud until the officer instructs him or her to stop.

During the one-leg stand test, the officer will look for the following signs of impairment. If the officer identifies at least two signs, the driver is likely too drunk to drive.

• The driver sways while balancing.
• The driver uses his or her arms to balance.
• The driver hops to maintain balance.
• The driver puts his or her foot down.

If you are facing criminal charges for driving under the influence, contact a Tacoma DUI lawyer. Your lawyer can help you navigate your legal options and work toward the best possible outcome.