What is the primary purpose of conducting HGN tests during a sobriety check?

The primary purpose of conducting Horizontal Gaze Nystagmus (HGN) tests during sobriety checks is to assess potential alcohol impairment. The HGN test evaluates the involuntary eye movements that can occur when a person is intoxicated. When someone consumes alcohol, it can affect their central nervous system, leading to observable physical signs, one of which is nystagmus—specifically, the inability of the eyes to smoothly follow a moving object. Law enforcement officers are trained to look for specific indicators during the HGN test, such as the onset of nystagmus at certain angles and the distinctiveness of the nystagmus at maximum deviation. These indicators help determine whether a person is likely impaired by alcohol, which is critical in the context of traffic safety and law enforcement. Thus, the focus on assessing impairment directly relates to the effectiveness of the sobriety check and the safety of individuals on the road.