What does an officer primarily rely on during the SFST?

During the Standardized Field Sobriety Test (SFST), an officer primarily relies on standardized clues and observations. These clues are well-defined behaviors and performance criteria established through research that indicate impairment due to alcohol or drugs. The SFST consists of three standardized tests: the Horizontal Gaze Nystagmus (HGN), the Walk-and-Turn (WAT), and the One-Leg Stand (OLS). Officers are trained to observe specific indicators during these tests, such as balance, coordination, eye movement, and the ability to follow instructions. These observations help the officer form an objective basis for determining whether a driver is impaired, rather than relying on subjective factors like intuition or community complaints. The structured nature of the SFST allows for consistent and reproducible results, which are essential for evaluating potential DUI cases accurately.