What does HGN stand for in the context of the Standardized Field Sobriety Test?

In the context of the Standardized Field Sobriety Test, HGN stands for Horizontal Gaze Nystagmus. This test is designed to evaluate an individual's eye movements as a way to determine impairment usually due to alcohol consumption. During the HGN test, an officer will observe the eyes of a suspect as they follow a moving object horizontally; the presence of nystagmus, which is an involuntary jerking of the eyes, can indicate that a person may be under the influence.

This test is significant because research has shown strong correlations between the angle at which nystagmus occurs and blood alcohol concentration levels. Understanding the nuances of HGN allows law enforcement officers to make more informed decisions regarding a person's level of impairment. The other options, while they include elements related to gaze or movement, do not define the HGN test correctly or relate to established protocols in sobriety testing.