Which SFST clue involves the subject stepping off the line?

The Walk-and-Turn test is specifically designed to evaluate a subject's ability to follow directions and maintain their balance while walking in a straight line. One of the key clues that law enforcement officers look for during this test is whether the subject steps off the line. This behavior can indicate a lack of balance, coordination, or focus, which are potential signs of impairment.

During the Walk-and-Turn test, subjects must walk heel-to-toe along a predetermined line, turn on one foot, and return in the same manner. Stepping off the line demonstrates difficulties in maintaining a straight path, a critical aspect of the test aimed at assessing motor skills and cognitive understanding of the task.

The other tests mentioned do not primarily focus on maintaining balance and following a straight line. For instance, the One Leg Stand involves balancing on one leg without stepping off, while the Horizontal Gaze Nystagmus assesses eye movement for signs of impairment. The Finger to Nose test evaluates coordination but does not involve a line or stepping off of it. Thus, the characteristic of stepping off the line is unique to the Walk-and-Turn test, making it the correct choice.