The Importance of Medically Clearing an Individual Before Administering the Horizontal Gaze Nystagmus Test

Since 1975, the National Highway Transportation Safety Administration (NHTSA) has standardized field sobriety tests for officers. Prior, each officer would administer their own test, or individual police stations would train their officers in specific tests to give to the motoring public. Today, there are three standardized tests of dubious veracity that are used universally by law enforcement across the country. One of those tests is the Horizontal Gaze Nystagmus (HGN). The HGN is considered the most accurate of the three standardized field sobriety tests performed by law enforcement. In this article, the Roswell, Georgia DUI defense attorneys at Andrew L. Schwartz, P.C. will discuss the HGN and how it works.

What is the Horizontal Gaze Nystagmus test? 

The HGN is one of three standardized field sobriety tests that are administered by law enforcement during a DUI stop. These field sobriety tests are considered (far) less accurate than mechanical testing devices such as breathalyzers or blood tests. They are generally used to give an officer probable cause to either administer the breathalyzer test or make an arrest based on the suspect’s conduct.

The HGN is considered the “most accurate” of all the field sobriety tests, but there are serious problems with the test, and it won’t work on everyone.

Medically qualifying a suspect for the Horizontal Gaze Nystagmus test

HGN is the involuntary jerking of the eyes as they look to the side. Ten steps exist for an officer to correctly administer the test. If the test is not administered according to the NHTSA guidelines, it’s likely compromised and inadmissible.

To begin the test, an officer positions a stimulus (pen, light, or finger tip) about 12-15 inches before the suspect’s face and slightly above eye level. If the stimulus is held too high, it can result in a false positive.

Next, the officer must medically qualify an individual for the HGN test. They do this by checking their resting Nystagmus (the involuntary jerking of the eyes as they look straight ahead). Next, the officer will check for equal pupil size. The pupils must be equal to administer the test. The last step is checking for equal tracking. The officer must move the stimulus at a rate that takes approximately two seconds from the center of the suspect’s face to the point that the eye can no longer move (maximum deviation) to the suspect’s left. The officer then moves the stimulus all the way to the maximum deviation on the suspect’s right. This is completed twice. It is important for the officer to medically qualify an individual before checking for clues. Failure to do so will likely mean that the test is inadmissible in court.

Talk to a Marietta, GA, DUI Attorney Today 

If you’re facing charges of DUI in Cobb County, GA, you’ll want the help of a skilled attorney to handle the charges. Call the Cobb County criminal defense lawyers of Andrew L. Schwartz, P.C., today to schedule an appointment and learn more about how we can help.