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DUI » DUI Testing » Field Sobriety Tests » Horizontal Gaze Nystagmus (HGN)

Horizontal Gaze Nystagmus Test

The word nystagmus is defined as a rapid and involuntary side-to-side jerking motion of the eye. The term comes from Greek nustagmos meaning “drowsiness.” The Horizontal Gaze Nystagmus (HGN) test is a Standardized Field Sobriety Test that involves having a suspected drunk driver follow an object or light with the eyes to determine whether they jerk involuntarily, as this is considered to be a sign of intoxication. In normal circumstances, the eye jerks only at high peripheral angles. When a person has a significant amount of alcohol in his or her system, the jerking may occur when the eyes try to track a moving object. The Horizontal Gaze Nystagmus is administered by having the subject slowly follow an object or light, such as a pen, finger or small flashlight, with the eyes.

The person administering the test will look for the following indicators of failure:

  • The eye cannot smoothly follow the moving object
  • Significant jerking is present in the eye when it is at maximum deviation
  • The jerking begins when the eye is within 45 degrees of center

The person administering the test will look for these indicators in each eye. If he or she observes four or more indicators between the two eyes, the subject may have a blood alcohol concentration of 0.08 percent or greater. According to tests conducted by Stuster and Burns for the National Highway Traffic Safety Administration (NHTSA) in 1998, the HGN test is accurate approximately 88% of the time.

Did you “fail” the Horizontal Gaze Nystagmus test?

Though you may have “failed” the Horizontal Gaze Nystagmus and were subsequently arrested for DUI, this does not necessarily mean that the test was right. Even the NHTSA recognizes that the HGN may indicate that the subject has taken seizure medications. There is the possibility that some other factor affected the outcome of your test, such as a physical condition, medication or an improperly administered test. Your DUI defense lawyer will thoroughly review every aspect of your testing to determine how to challenge the results. Contact our firm today to learn more about the Horizontal Gaze Nystagmus and how this may affect your case.

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