During the HGN test, what should the driver follow with their eyes?

During the Horizontal Gaze Nystagmus (HGN) test, the officer asks the driver to follow a small object with their eyes, typically a pen or a finger. This test is designed to assess the driver's eye movement and is used to detect signs of impairment, particularly due to alcohol or drugs. When a person is under the influence, their eye movements may not track smoothly or may exhibit nystagmus, which is an involuntary jerking of the eyes.

The use of a small object is crucial because it provides a clear point for the driver to fixate on, ensuring that the assessment is effective. The specific choice of a small object rather than other options, such as a flashlight or a pattern on the ground, is due to the need for a controllable and visible target that is easy to follow. This aids in the measurement of the driver's eye movement without distraction, allowing for a more accurate evaluation of their potential impairment.