How is body posture relevant during the HGN test?

Body posture is vital during the Horizontal Gaze Nystagmus (HGN) test because a relaxed and stable posture contributes to the reliability of the results. When the subject maintains a natural and steady position, it allows for a clearer observation of involuntary eye movements. Such movements can indicate potential impairment, often associated with alcohol consumption or other substances. If the subject is tense or unstable, it may introduce additional variables that could obscure the test results. Therefore, ensuring that the subject is comfortable and stable during the HGN assessment directly influences the accuracy and effectiveness of the test.