How is HGN utilized in field sobriety tests?

The use of Horizontal Gaze Nystagmus (HGN) in field sobriety tests focuses on assessing the level of impairment based on eye movements. This technique involves observing the eyes as they follow a moving object, typically a pen or flashlight. When a person is under the influence of alcohol or certain drugs, their eye movements can exhibit specific characteristics such as involuntary jerking or a lack of smooth pursuit. These abnormal eye movements are indicative of impairment.

Law enforcement officers are trained to recognize these signs, which serve as a visual cue to evaluate a person’s level of intoxication. The presence of HGN is one of the indicators used alongside other tests to build a comprehensive picture of a driver's impairment. By analyzing how the eyes react, officers can make informed decisions about the suspect's level of sobriety and the potential need for further actions, like an arrest or additional testing. This method is scientifically validated and widely accepted in the standardized field sobriety testing protocol.