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What Is Horizontal Gaze Nystagmus (HGN)?

When an individual is stopped for suspicion of driving under the influence of alcohol, police officials may require them to take a field sobriety test. One of the three main components of the sobriety test involves horizontal gaze nystagmus (HGN). During the HGN step, police officers look for involuntary jerking of the individual’s eye when it gazes to the side. It is typical for there to be an exaggeration in jerking of the eyes when a person consumes too much alcohol.

How Horizontal Gaze Nystagmus (HGN) Works?

Since alcohol suppresses the nervous system, it is difficult to make eye movements that are smooth and accurate. For such reasons, police officers tend to look for exaggerated eye jerks to determine if there is alcohol in an individual’s system.

The police officer often tells the driver that they are going to check their eyes and asks them if they wear contact lenses or have medical issues that would affect results. Then they ask the driver to follow an object with their eyes (typically a pen) and place it twelve to fifteen inches away from their eyes. The police officer will use a flashlight to determine if there is sudden jerking of the eyes.

Are Horizontal Gaze Nystagmus (HGN) Tests Reliable?

According to the National Highway Traffic Safety Administration (NHTSA), field sobriety tests show accurate blood-alcohol concentration (BAC) of .10 percent or higher 83 percent of the time. However, it is important to note that an HGN test is only a physical observation by the officer, which would highly depend on the officer’s level of training. Although it is found to have accurate results, the HGN test alone isn’t sufficient evidence to prove drunk driving.

If you face DUI charges, you only have 15 days to act before your license is suspended. Contact our Phoenix DUI defense lawyers today at (602) 842-6762 to schedule a consultation!

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