During the Horizontal Gaze Nystagmus (HGN) test, which eye is assessed first?

The Horizontal Gaze Nystagmus (HGN) test is a key component of the Standardized Field Sobriety Test (SFST) used to assess a driver's level of impairment due to alcohol or drugs. This test specifically evaluates the involuntary jerking of the eyes, known as nystagmus, as they move horizontally.

The protocol for the HGN test dictates that the left eye is assessed first. This approach ensures consistency in testing procedures and helps to minimize any potential bias in the results. By starting with the left eye, officers can maintain a standard method for evaluating nystagmus and interpreting the findings, which is crucial for effective sobriety assessments.

Understanding the correct sequence of events in the HGN test is vital for law enforcement officers and those involved in DUI enforcement, as accuracy and standardization are essential in court proceedings and when making judgments about a suspect’s sobriety. Starting with the left eye allows officers to develop a methodical approach to identifying signs of impairment, ultimately leading to more reliable results.