The Horizontal Gaze Nystagmus (HGN) Test is a field sobriety test commonly used by law enforcement officers to detect signs of impairment due to alcohol or certain drugs. Nystagmus refers to the involuntary jerking or bouncing movement of the eyes, which can become more pronounced when a person is under the influence.


During the HGN test, an officer will typically use a stimulus, such as a pen or small flashlight, and ask the driver to follow it with their eyes while keeping their head still. The officer will move the stimulus horizontally across the driver's field of vision, looking for specific eye movements that indicate impairment.


The three indicators that the officer is typically looking for during the HGN test are:


  1. Lack of Smooth Pursuit: The officer checks whether the eyes smoothly track the stimulus as it moves horizontally. If the eyes show distinct jerking or are unable to smoothly follow the stimulus, it may suggest impairment.

  2. Nystagmus at Maximum Deviation: The officer checks for the presence of nystagmus when the eyes are looking as far to the side as possible. In this position, nystagmus tends to be more noticeable if the person is impaired.

  3. Onset of Nystagmus Prior to 45 Degrees: The officer determines if nystagmus is observed when the eyes are still moving but have not reached a 45-degree angle from the center. If nystagmus occurs at a lesser angle, it could indicate impairment.

It's important to note that the HGN test, like other field sobriety tests, is not 100% accurate in determining a person's level of impairment or their exact blood alcohol concentration (BAC). The results of the HGN test are subjective and can be influenced by factors such as the officer's experience, the driver's medical conditions, or environmental factors.


If an officer believes that a driver has failed the HGN test or shows signs of impairment, they may proceed with additional testing, such as a breathalyzer test or blood test, to gather more evidence of intoxication.


If you find yourself in a situation where you have been subjected to an HGN test or any other field sobriety test and are facing legal consequences, it is recommended to consult with a lawyer who specializes in DUI/DWI cases. They can provide guidance and help protect your rights under the laws of your jurisdiction.



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