What does impaired eye muscle functioning indicate during the HGN test?

Impaired eye muscle functioning during the Horizontal Gaze Nystagmus (HGN) test is significant because it is typically correlated with the presence of alcohol impairment. The HGN test specifically assesses the involuntary eye movement that occurs when a person gazes to the side. When a person is under the influence of alcohol, their ability to control their eye muscles can be affected, leading to distinct signs such as nystagmus (the jerking motion of the eyes).

The signs observed during the HGN test, especially when they exceed the normal physiological response levels, can serve as indicators of alcohol intoxication. Officers trained in administering the HGN test look for specific markers, such as the angle at which the nystagmus begins, to evaluate the extent of impairment. Hence, when someone exhibits impaired eye muscle functioning during this test, it strongly suggests a higher likelihood of alcohol impairment. Recognizing this connection allows law enforcement to make informed judgments regarding a driver’s ability to operate a vehicle safely.