What happens during the HGN testing process?

During the HGN testing process, the officer focuses on assessing the eye movements of the subject as they follow a stimulus, such as a pen or a finger, moving horizontally. This test is designed to determine whether nystagmus, which is an involuntary jerking of the eyes, is present. The presence of horizontal gaze nystagmus can indicate impairment, often associated with intoxication or certain medical conditions. The officer looks for specific signs, such as the angle at which the nystagmus begins and the smoothness of the eye tracking, which are used to help evaluate the subject's level of impairment due to alcohol or drugs.

The other options—conducting a conversation, assessing physical fitness, and asking for a breath sample—are not part of the HGN test process and serve different purposes in a field sobriety assessment. Each of these serves to gather information or evidence but does not specifically measure the involuntary eye movements that are central to the HGN evaluation.