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When Your HGN Test Results May Get the Side-Eye in Court

Jeff Cole
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Partner at Zimmer, Duncan & Cole

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There are many ways that a law enforcement officer may try to determine if you are intoxicated. Turn on any police reality show and you will see dozens of different tests being performed on the side of the road, from walking a white line to saying the alphabet backwards.

What Is the Horizontal Gaze Nystagmus Test?

One of the official tests that a police officer may administer you is the HGN, or Horizontal Gaze Nystagmus test. This test evaluates an involuntary twitch in a person’s eye as it follows a pen or penlight when it switches from standard to peripheral vision; in people who may be intoxicated, the eye will twitch at smaller angle of deflection and the eye’s movement may not be smooth.

For officers who are trained in the administration of this test, it can be a very accurate way to tell if a person could be impaired. What it is not, however, is a blood alcohol concentration (BAC) test to determine exactly how impaired you may be. You cannot be arrested based on your HGN results alone; it can only serve as an indicator that you are impaired, prompting a BAC test.

Why the HGN Test May Not Be Very Reliable

Many officers, however, are not very skilled at the HGN test. Because of this, courts are often hesitant to use HGN results as evidence in a DUI case. Most officers only enter it as the probable cause for administering a BAC test; in some instances, however, you may be able to dispute its inclusion entirely.

If you were wearing glasses during your test, or if you face was not illuminated properly, you may be able to argue that the officer did not have a clear view of your eyes to accurately judge your nystagmus. Another common mistake officers make is administering the test while you are facing oncoming traffic and headlights, which would possibly skew your results.

There Is Help Available

If you have been charged with a DUI in South Dakota and they have entered your HGN results as evidence against you, you may be able to argue this particular piece of evidence. Reach out to our firm now by clicking on the live chat link, and learn how our firm may be able to assist you.


Category: Criminal Defense


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