Which SFST is typically the first test administered during a DUI investigation?

The Horizontal Gaze Nystagmus (HGN) test is typically the first standardized field sobriety test administered during a DUI investigation. This test is particularly effective for assessing impairment due to alcohol consumption and is based on the observation of involuntary eye movements known as nystagmus.

The HGN test involves the officer checking the subject's eyes for nystagmus while following a stimulus, such as a pen or a finger, a few inches from the subject's face. The officer looks for specific indicators: the presence of nystagmus at maximum deviation, the degree of nystagmus prior to 45 degrees, and the ability of the subject to follow the stimulus smoothly. These indicators provide objective measures that suggest whether a driver may be under the influence of alcohol.

By starting with the HGN test, officers capitalize on its high reliability for detecting alcohol impairment, making it a practical initial assessment before proceeding to more complex tests like the Walk-and-Turn or One-Leg Stand tests. It also allows officers to gather visual evidence early in the investigation, which can be crucial for establishing impairment.