In the context of DUI testing, what does HGN stand for?

The correct answer, Horizontal Gaze Nystagmus, refers to a specific type of eye movement that is evaluated during field sobriety testing for suspected driving under the influence. HGN tests are designed to observe the involuntary jerking of the eyes as a person gazes to the side. This type of nystagmus is typically more pronounced in individuals who are impaired by alcohol or certain drugs.

During the test, an officer will direct the suspect to follow a stimulus, such as a pen or flashlight, with their eyes while keeping their head still. The presence of HGN can indicate impairment, as the smoothness of the eye's movement can be adversely affected by substances. The assessment of HGN is a crucial part of the Standardized Field Sobriety Tests (SFST), which are standardized protocols implemented to assess a driver’s level of intoxication.

This term is not to be confused with the other options listed. For instance, "Horizontal Gravitational Nystagmus" and "High Gaze Nystagmus" do not represent established terms used in DUI testing, and "Head Gaze Nystagmus" misstates the function of the test, which specifically assesses lateral (horizontal) gaze, rather than movement