Police may use field sobriety testing when they suspect that you are driving under the influence of alcohol. One commonly used assessment involves observing your eye movements while you follow an object from side to side.
The Horizontal Gaze Nystagmus test looks for involuntary jerking of the eyes that may become more noticeable with alcohol impairment. Understanding how officers administer the test can help you understand how the results may become evidence in a drunk driving case.
Officers first check your eyes
Before beginning the test, an officer typically checks whether your eyes appear suitable for testing. You may be asked about contact lenses, eyeglasses or medical conditions that could affect your eyes.
The officer may also examine your pupils and determine whether both eyes track together. Resting nystagmus or unusual eye movement can indicate that factors other than alcohol could influence the observations.
You follow an object with your eyes
The officer generally holds a stimulus, such as a pen or penlight, approximately 12 to 15 inches from your face and slightly above eye level. You are instructed to keep your head still and follow the object using only your eyes.
Lighting and positioning matter because flashing patrol lights and other visual distractions can potentially interfere with observation.
Police look for three clues
The officer moves the stimulus across your field of vision while watching each eye for specific responses.
- First, the officer checks whether your eyes smoothly follow the moving object. Jerking rather than smooth movement may count as a clue.
- Second, the officer moves the stimulus toward the outer edge of your vision and holds it there. Distinct and sustained jerking at maximum deviation is another clue.
- Third, the officer watches for nystagmus beginning before your eye reaches approximately 45 degrees from the center of your face.
How the officer administered and interpreted the test can therefore matter when evaluating Georgia drunk driving charges. If you believe an HGN test was performed incorrectly or its results contributed to your arrest, seek legal guidance about the evidence, testing procedures and available defense options.