During the Horizontal Gaze Nystagmus test, what is the officer looking for?

During the Horizontal Gaze Nystagmus (HGN) test, the officer is specifically looking for involuntary eye movement. HGN is a physiological phenomenon where the eyes exhibit an inability to smoothly track a moving stimulus, in this case, a pen or flashlight being moved horizontally. When a person is under the influence of alcohol, this involuntary nystagmus can become more pronounced, making it a useful indicator of impairment. The test involves observing the eyes as they follow the moving object to identify the presence and intensity of nystagmus, which can indicate levels of intoxication.

The other options focus on different physical aspects such as speech, walking coordination, and balance, which are assessed in other fields sobriety tests but are not the focus of the HGN test. This specificity makes the HGN effective for gauging impairment due to substances, particularly alcohol.