Field sobriety tests and operating while intoxicated test one: Horizontal Gaze Nystagmus

Test one: Horizontal Gaze Nystagmus

The holiday season is upon us. With the holiday season comes holiday parties. Many times, those holiday parties involve alcohol. If you’re pulled over on suspicion of OWI, an officer may ask you to step out of your vehicle and submit to field sobriety tests. This is part one of a three-part series to provide you more information on what those field sobriety tests are and what officers are looking for. The first test is the Horizontal Gaze Nystagmus or HGN.

What is it?

When an officer has reasonable to suspicion to believe you may be operating while intoxicated (OWI also known as DUI), he or she may request you step out of your vehicle to perform what are known as the field sobriety tests (FST). These tests were developed by the National Highway Traffic Safety as tools for police to use when suspecting someone of OWI. Officers look for “clues”, which are indicators of impairment, in order to form probable cause to make an arrest.

Typically, the first thing an officer will look for when administering these tests is any sort of nystagmus. Nystagmus is the involuntary jerking or bouncing of the eyes. Because this is an involuntary action controlled by a person’s central nervous system, there is no way to “fake” this type of behavior or otherwise cover up its existence.

Officers most commonly look for nystagmus by administering the horizontal gaze nystagmus (HGN) test.

How is it administered?

Before beginning the HGN test, officers should check to make sure you are not suffering from any injuries. They do this by observing pupil size, whether your eyes track together and whether your eyes exhibit nystagmus when staring straight ahead. In this test, an officer holds an object, typically a pen or finger, out from your nose 12-15 inches and moves the object from left to right. Officers are looking for three distinct clues when administering this test.

Lack of smooth pursuit

First, officers look for is a “lack of smooth pursuit” which is seen as jerking or bouncing of the eyes when they try to follow a moving object. Typically when not impaired by alcohol, your eyes will track smoothly (imagine a marble rolling across the floor). However, alcohol can cause an eye to bounce or jerk when tracking an object back and forth. This is the first clue officers look for as a sign of impairment.

Sustained nystagmus

Second, officers look for “distinct and sustained nystagmus at maximum deviations.” This occurs when an officer holds the object out to the side as far as the eye can see it. The object should remain for at least four seconds for the officer to observe the eye jerking toward the side. This is the second clue officers look for as a sign of impairment.

Onset prior to 45 degrees

Third, officers will look for the “onset of nystagmus prior to 45 degrees”. This means an officer will look for the exact moment the nystagmus starts in the eye. Studies show if a person is impaired at above a .08%, nystagmus will be present prior to 45 degrees. This is the third clue officers look for as a sign of impairment.

Charged with a DUI? Get help today

This test is only reliable if administered properly and there are a plethora of ways to challenge the accuracy of this and other FSTs. If you are charged with an OWI, you need a dedicated and skilled legal defense on your side. At Grewal Law, PLLC, our attorneys will help you understand the tests administered in your case and review any flaws in the administered FSTs. We also will work to make sure your rights are protected. Contact us today to help with your DUI charges.

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