Which key factor is checked to understand a subject's performance in sobriety tests?

Motor skills are the key factor checked to evaluate a subject's performance in sobriety tests. Standardized Field Sobriety Tests (SFST) are designed to assess an individual's physical coordination and balance, which are critical aspects of motor function. During these tests, law enforcement officers observe how well a subject can perform tasks that require precise motor skills, such as walking straight, standing on one leg, and following a moving object with their eyes. Impairment in motor skills is often an indicator of alcohol or drug influence, as these substances can significantly affect physical coordination and reaction times.

Emotional stability, short-term memory, and mathematical ability, while potentially influenced by alcohol or drugs, are not primary indicators used in the SFST framework. The tests focus specifically on the observable physical abilities that can demonstrate impairment during activities that involve coordination and balance.