What is the purpose of administering the HGN test?

The purpose of administering the Horizontal Gaze Nystagmus (HGN) test is to gauge impairment due to alcohol consumption. During this test, law enforcement officers observe the involuntary jerking of the eyes as they follow a moving object, typically a pen or flashlight. This involuntary eye movement is exacerbated when a person is under the influence of alcohol, particularly at higher blood alcohol concentration levels.

The HGN test is a standardized field sobriety test that provides officers with valuable information about a person's impairment. This test specifically targets the effects of alcohol on the nervous system, as alcohol can affect balance and coordination, leading to noticeable eye movements that are not present in sober individuals. By analyzing the results of the HGN test, officers can make informed decisions regarding a suspect's level of impairment related to alcohol consumption.