What does nystagmus refer to in the context of field sobriety tests?

Nystagmus refers specifically to the involuntary jerking or rapid movement of the eyes, which is a significant indicator in field sobriety tests. This phenomenon can be observed when a person is asked to follow an object with their eyes; a trained officer can assess the movement of the eyes as they track the object.

In the context of standardized field sobriety tests, nystagmus is particularly relevant because its presence can suggest impairment due to alcohol or other drugs. The Horizontal Gaze Nystagmus (HGN) test is a common assessment tool where the officer checks for nystagmus while the subject follows a stimulus (usually a pen or finger) horizontally. If significant nystagmus is observed, it may indicate a higher blood alcohol concentration or impairment.

The other options touch on physical coordination and balance, which are certainly important aspects in determining impairment, but they do not directly relate to the specific definition of nystagmus as it applies to these tests. Thus, understanding nystagmus is vital for interpreting behaviors that may indicate impairment.