What should an officer observe during the HGN test?

During the Horizontal Gaze Nystagmus (HGN) test, the officer is specifically looking for distinct and sustained nystagmus at maximum deviation. This refers to the involuntary jerking of the eyes that can occur when a person is under the influence of alcohol or certain drugs. Distinct nystagmus is characterized by a clear and noticeable jerking of the eyes as they are moved toward the side at maximum deviation, which occurs when the eyes are turned to the farthest point they can go. Sustained nystagmus indicates that the jerking is maintained for at least four seconds at the extreme angle, which further supports the observation that the subject may be impaired.

The other options do not focus on the critical indicators of impairment that the HGN test is designed to assess. The ability to maintain eye contact and pupil size are not direct measures of nystagmus and do not provide as definitive evidence of impairment as the specific observations outlined in the HGN test. The speed of eye movement, while it may seem relevant, does not directly address the characteristics of nystagmus that are crucial for this test's conclusions. Therefore, option A effectively captures the key aspects that an officer needs to observe when administering the H