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What is HGN?

HGN refers to the Horizontal Gaze Nystagmus Test. The test is a field sobriety test that is given by law enforcement when someone is suspected of driving under the influence of drugs and/or alcohol.  The HGN test checks for Horizontal Gaze Nystagmus, which is an involuntary jerking or twitching of a person’s eyes that naturally happens when your eyes look to the side.  Normally, nystagmus happens only when you are rotating your eyes to look out to the sides and then only at extreme angles (typically more than 45 degrees).  However, if you have been drinking and are impaired by the alcohol consumption, nystagmus is exaggerated and can happen even if you are not looking out at an angle to the sides.

The HGN test is used to watch for the nystagmus, which is a jerking or twitching of the eyes.  If law enforcement sees nystagmus, then you may be asked to perform additional field sobriety tests or you may be asked to submit to a breath or a blood test. The State of Minnesota like to have you believe that the HGN tecan correctly classify someone as drunk or sober and cite to a study in which 88 percent of cases in the 1998 study conducted by Stuster and Burns was correctly identified.  However, a few interesting things about that study are that it was funded by the National Highway Traffic Safety Administration and they are the ones who do the training and certification for police officers in this area of the law. There has been a great deal of criticism leveled at the HGN  that it However, you are not necessarily obligated to agree to take the HGN test and the test may not be admissible to be used against you in a court of law.


An experienced drunk driving lawyer can help you to better understand your rights when it comes to the HGN test and can assist you in understanding the impact the test has on your case.

The HGN Test

When police perform an HGN test, you generally will be asked to follow a slow moving object horizontally with your eyes. For example, police may hold a flashlight or a pen in front of your eyes and move it from side to side, asking you to follow it. The officer will then watch your eyes as you try to follow the object. The police will be on the lookout for:

  1. Whether the eye is able to smoothly follow the object or not.
  2. Whether your eye begins to jerk when your eyes are turned to the sides.
  3. Whether the jerking of the eye begins within 45 degrees of your eyes looking front and center.

If your eyes are jerky (especially close to center) and/or are not able to smoothly follow the object, this can be a sign of alcohol impairment. HGN can also occur when other drugs have been taken including seizure medicine; inhalants; phencyclidine; barbiturates and depressant medications. A failed HGN test, therefore, can be used as evidence of either drugged driving or sober driving.

Since an HGN test could potentially be used against you, you may wish to refuse this test. A refusal, however, could result in police requiring that you submit to a test of your blood alcohol content. If you decline to have your BAC tested, this could potentially result in a license suspension.  Still, in many cases, refusing the HGN test does make sense.

You should speak with an experienced drunk driving lawyer to better understand the impact of an HGN test on your DWI case and to learn what options you have if law enforcement indicates that you failed an HGN test.