At what angle is the onset of nystagmus considered a clue?

The onset of nystagmus at an angle of 45 degrees is significant because it helps law enforcement officers identify potential impairment in a driver due to alcohol or drug use. Nystagmus refers to the involuntary jerking motion of the eyes, and the observation of this condition provides crucial evidence when assessing a suspect's level of intoxication.

During field sobriety tests, particularly the Horizontal Gaze Nystagmus (HGN) test, officers look for the angle at which eye jerking first becomes apparent. If this occurs at 45 degrees or less, it often suggests a high level of intoxication or impairment because it indicates that the central nervous system is affected. The 45-degree angle serves as a benchmark in the training of officers, providing a clear point of reference during assessments. Recognizing this sign plays a vital role in the decision-making process surrounding DUI enforcement.