DUI/DWI Field Sobriety Tests

When someone is pulled over for being suspected of Driving Under the Influence (DUI) or Driving While Intoxicated (DWI) they may be asked to perform a series of tests to help determine whether or not they are intoxicated. There are three different tests that were developed and standardized by the National Highway Traffic Safety Administration and the Southern California Research Institute. Because these three tests have been researched and standardized they are given a great deal of credibility in court.

The Horizontal Gaze Nystagmus

Nystagmus describes a bouncing eye motion that is involuntary. Normally, when a person is not under the effects of alcohol, the eye will move smoothly, like a marble moving over glass. An eye that is exhibiting nystagmus will jerk like a marble rolling over sandpaper. Additionally, an alcohol-impaired person usually will have difficulty tracking a moving object, like a pen or a flashlight.

When performing this test, a police officer will have the subject follow an object with their eyes while the officer observes their eye motions. The object will be held twelve to fifteen inches from the subject’s face and slightly above eye level. The officer will explain that the subject should follow the object with their eyes while keeping their head still.

The police officer will check for medical impairment that might affect the HGN test by verifying that both eyes can follow an object moving quickly across their field of vision and that both pupils are the same size. If the subject does not have equal pupil size it can indicate blindness in one eye or another disorder. If the subject cannot follow the object with both eyes or has uneven pupil size, the HGN test should be discontinued.

The Walk-And-Turn

The walk-and-turn test is known as a “divided attention” test. This means that it requires a subject to listen and follow instructions while performing the required tasks. A person who is not under the effects of alcohol or drugs can easily divide their attention between physical and mental activities, while an intoxicated person will have difficulty.

For the walk-and-turn test the subject is instructed to take nine heel-to-toe steps along a straight line, then to turn on one foot and take nine more heel-to-toe steps in the opposite direction. There are seven indicators that the subject is impaired:

• Losing balance while listening to the instructions
• Beginning before the instructions are finished
• Doesn’t touch heel-to-toe
• Using arms for balance
• Stopping to regain balance
• Losing balance while turning
• Loses count of steps or takes the incorrect number of steps in each direction

The One-Leg Stand

The one-leg stand test is another “divided attention” test. In the one-leg stand test the subject is instructed to stand on one foot and to hold the other foot approximately six inches above the ground. They are then instructed to count aloud until they are told to put their foot down. The police officer will time the subject for thirty seconds, while looking for the following indicators of impairment:

• Using arms for balance
• Hopping
• Swaying to balance
• Putting their foot back on the ground

The more indicators observed by the police officer during the tests, the more compelling the results of the three tests will be in court. If the subject is disabled and cannot perform the standardized tests there are other tests that can be performed like reciting the alphabet backwards or touching their fingers to their nose, but because those tests haven’t been tested or standardized, they are generally not admissible in court.

This article is for informational purposes and does not constitute legal advice. Please contact an attorney in your local area for more information about DUI/DWI Law.

Related Legal Website: The Law Offices of Michael Lowe. Serving DUI clients in Dallas, TX.