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Suwanee GA DUI / DWI Blog

Sunday, January 7, 2018

In Focus: The Horizontal Gaze Nystagmus Test and How to Challenge It

Is the DUI eye gaze test reliable?

The Horizontal Gaze Nystagmus (HGN) Test is one of the most common tests administered when a driver is pulled over on suspicion of drunk driving.  Commonly known as the “eye test,” the HGN test involves a qualified police officer moving a light or pen in front of the suspect’s eyes and requesting that the driver follow the light.  While the test sounds simple on the surface, it is a complex test that must be administered carefully and accurately in order to be accurate.  Anyone charged with a DUI on the grounds of the HGN test will want to learn more about how you can challenge the evidence. 

The Basis Behind the HGN Test

The HGN test is said to evaluate a driver’s level of impairment due to alcohol based on a fact of human biology.  When a person looks sideways at an angle of over 45 degrees, they will experience an involuntary twitch.  However, those who are intoxicated will exhibit a twitch when a light is held at less than 45 degrees.

The National Highway Traffic Safety Administration (NHTSA) has determined that, in its opinion, the HGN test is reliable, but only if performed correctly on a driver that is medically qualified to undergo the test.  Mistakes made in the administration of the test could lead to inaccurate results that should not be admitted against you in court.  Some states have actually ruled to not admit the results of the HGN test into evidence, even though they can still be used as a basis for an arrest.

Challenging the HGN Test 

In administering the HGN test, the trained police officer must observe the following:

  • The officer must ask the driver to remove his or her glasses and should note whether the driver has contacts, though the contacts can remain in place;
  • The driver should be instructed to put his or her feet together and hands by the side.  The driver will then be asked to follow a stimulus with both eyes while keeping their head in place;
  • The officer must hold the light or stimulus between 12 and 15 inches from the driver’s face, with it positioned slightly above eye level;
  • The stimulus will be passed at least 14 times.

Common grounds for challenging the test include evidence that the officer moved the stimulus too quickly, held it too close or far away, or did not move the stimulus correctly.  Your DUI defense attorney will review the evidence and determine whether you have a viable challenge to the HGN test. 


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| Phone: 770-284-1319

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