Roadside Exercises Are Not Simple Pass-or-Fail Tests
The standardized battery commonly includes Horizontal Gaze Nystagmus, Walk-and-Turn, and One-Leg Stand. Officers look for specific clues, but the significance of those clues depends on proper administration and the surrounding conditions.
Alphabet, finger-to-nose, counting, and similar exercises may be non-standardized tests and should not be confused with the standardized three-test battery.
Horizontal Gaze Nystagmus
The officer moves a stimulus and looks for lack of smooth pursuit, sustained nystagmus at maximum deviation, and onset before 45 degrees.
- Correct stimulus distance and speed matter
- Medical or neurological causes should be considered
- The officer should document the clues in each eye
Walk-and-Turn
The person is asked to maintain a position, follow multi-step instructions, walk heel-to-toe, turn, and return while the officer looks for standardized clues.
- Surface, footwear, weather, traffic, and lighting matter
- Instructions and demonstration should be complete
- Video can confirm or contradict scoring
One-Leg Stand
The person raises one foot, watches it, and counts while the officer observes swaying, hopping, using arms, or putting the foot down.
- Age, injury, balance, and fatigue may matter
- The timing should be documented
- The exercise does not directly measure BAC
