How far should the stimulus be placed from the suspect’s nose during the HGN test?

During the Horizontal Gaze Nystagmus (HGN) test, the stimulus should be placed approximately 12-15 inches from the suspect’s nose. This distance is optimal because it allows for a clear view of the eyes while ensuring that the test can effectively measure the nystagmus, or the involuntary eye movement, often associated with impairment due to alcohol consumption or other substances.

At this range, the individual can comfortably focus on the stimulus, which facilitates the observation of eye movements for the examiner. If the stimulus is positioned too close, it may cause discomfort or a natural eye response inappropriate for the test. Conversely, placing the stimulus too far away may lead to an ineffective assessment, as the fine details of eye movement could become less discernible. Thus, maintaining the recommended distance is crucial for the accuracy and reliability of the test results.