What does "HGN" stand for in the context of field sobriety tests?

In the context of field sobriety tests, "HGN" stands for Horizontal Gaze Nystagmus. This is a specific eye movement test used by law enforcement officers to assess a suspect's level of impairment, particularly for alcohol consumption. During the HGN test, the officer observes the eyes of the subject as they follow a moving object, usually a pen or a finger, that is moved horizontally across their field of vision.

The key aspect of the HGN test is the identification of involuntary jerking of the eyes, which can be more pronounced with increasing blood alcohol concentration (BAC). The presence of nystagmus indicates a potential impairment, as alcohol and certain drugs can affect the central nervous system and the vestibular system responsible for eye movement control. This test is a critical component of the Standardized Field Sobriety Tests (SFST) protocol, as it provides objective data that contributes to the overall assessment of the suspect’s sobriety.