What does a strong indicator of impairment in the HGN test suggest about the subject's BAC?

A strong indicator of impairment in the Horizontal Gaze Nystagmus (HGN) test is associated with a Blood Alcohol Concentration (BAC) that is likely above 0.08. The HGN test measures the involuntary jerking of the eye as a person gazes to the side, which can be exacerbated by alcohol consumption. Research and field studies show that the typical onset of significant nystagmus occurs when a person's BAC reaches around or above this level, suggesting impairment.

When the test indicates pronounced nystagmus, it is a clear sign that the individual's faculties are compromised, and this level of impairment correlates with higher BAC levels, often above the legal limit of 0.08 in many jurisdictions, including Arizona. Therefore, the conclusion that a strong indicator of impairment suggests a BAC above this threshold is consistent with the accepted standards in DUI assessments.