What is the 2nd clue for impairment?

• A. Distinct and Sustained nystagmus at maximum deviation
• B. Resting nystagmus only
• C. Eye blinking frequency changes
• D. Pupil size changes

Answer: (A)

In the Horizontal Gaze Nystagmus test, you’re looking for specific eye-movement clues that reveal impairment. Nystagmus is the quick, involuntary jerking of the eyes, and impairment tends to make these jerks more noticeable. The second clue is distinct and sustained nystagmus at maximum deviation: as the eyes are held at the farthest point to one side, you’ll see a clear, lasting jerking motion rather than a smooth, steady gaze or a brief movement. This pattern is easier to detect when someone is impaired because alcohol or drugs disrupt the brain’s control of eye movements, especially near the ends of the gaze.

Resting nystagmus isn’t part of the HGN clues used in this test, and changes in eye blinking or pupil size aren’t the cues evaluated for impairment in the HGN portion.