Which of the following could impact a subject's performance on SFSTs aside from drugs or alcohol?

Fatigue can significantly impact a subject's performance on Standardized Field Sobriety Tests (SFSTs). When an individual is fatigued, their cognitive function and physical coordination may be diminished, leading to errors in tasks that require balance, concentration, and motor skills. This reduced ability can mimic or exacerbate the signs of impairment typically associated with the influence of alcohol or drugs.

While factors such as environmental temperature and time of year might influence a person's comfort or physical responses, they are not as directly related to cognitive and physical impairment as fatigue. Similarly, the choice of clothing can affect a subject's comfort during a field sobriety test, but it does not fundamentally alter their inherent ability to perform the tasks required in the test. Therefore, recognizing fatigue as a legitimate factor in SFST performance emphasizes the need for law enforcement officers to consider various influences beyond intoxicants when assessing a subject's state.