Understanding the Horizontal Gaze Nystagmus Test

When people are stopped in New Jersey on the suspicion that they are driving under the influence of alcohol, the officers may ask them to perform several standardized field sobriety tests. One of these tests is called the horizontal gaze nystagmus test, which is a test of the tracking movements of the eyes. Horizontal gaze nystagmus is jerking that happens with the eyes when people look to the side.

Officers administer the HGN test by asking people to focus on a pen they hold in one hand in front of their faces. The officers ask the people to keep their eyes focused on the pen as the officers slowly move it to the side of their visual ranges while the people keep their heads facing forward. Horizontal gaze nystagmus of the eyes is more pronounced in people who are under the influence of alcohol.

Officers look for three clues when they administer the HGN test. They check to see if the eyes are unable to smoothly pursue the object as it moves. They also check to see whether the person’s eyes show distinct jerking motions when they keep them to the side for four seconds. Finally, they check to see whether nystagmus occurs at a 45-degree angle.

When the HGN test is administered using the standards promulgated by the National Highway Safety Traffic Administration, the NHSTA says that it is 83% accurate. Officers do not always administer the test correctly, however. People who are facing drunk driving charges after failing the HGN test might benefit from having their tests reviewed by an experienced DUI defense attorney. The lawyer might review the officer’s report and any video of the administration of the SFSTs. If the attorney identifies problems, he or she may file a motion to seek suppression of the HGN and other SFSTs from the evidence.