What is meant by "distinct and sustained nystagmus"?

"Distinct and sustained nystagmus" refers to a specific type of eye movement that is characterized by clear and noticeable oscillations of the eyes. This term is crucial in the context of the Horizontal Gaze Nystagmus (HGN) test, which is utilized by law enforcement to help determine potential impairment due to alcohol or drug use. In this situation, "distinct" indicates that the eye movements are easily observable, while "sustained" means that the movements last for a certain duration and do not smooth out at maximum deviation – the point where the eye is turned as far to one side as it can go without discomfort.

This concept is essential because the presence of distinct and sustained nystagmus is one of the clues that can indicate a level of impairment. Identifying this particular type of eye movement during the HGN test provides officers with critical evidence in assessing whether a driver may be under the influence of substances, thereby helping ensure road safety.