What does a high score on the Horizontal Gaze Nystagmus test indicate?

A high score on the Horizontal Gaze Nystagmus (HGN) test indicates an increased likelihood of alcohol impairment. The HGN test assesses the involuntary jerking of the eyes as a person gazes to the side. When a person is under the influence of alcohol, this jerking can become more pronounced and occur at lesser angles than what is typical for sober individuals. Law enforcement officers use this test as part of their field sobriety testing because it can indicate the presence of alcohol in the bloodstream, correlating with higher blood alcohol content levels. The HGN test is designed to evaluate the neurological functions affected by alcohol, making a high score an indicator of potential impairment rather than suggesting the driver is not impaired or has improved reaction times. While certain medical conditions can affect HGN results, the primary interpretation in the context of DWI testing is related to alcohol impairment.