SFST One Leg Stand 3 — Questions and Answers
Question 1: What counting method is the subject instructed to use during the OLS test?
- Count from 1 to 30 silently
- Count out loud in the format 'one-thousand-one, one-thousand-two...' (Correct answer)
- Count backwards from 30
- Count to 10 and repeat three times
Correct answer: Count out loud in the format 'one-thousand-one, one-thousand-two...'
Subjects are instructed to count out loud saying 'one-thousand-one, one-thousand-two' up to 'one-thousand-thirty' so the officer can time the 30-second period.
Question 2: A person with a leg injury causing an uneven gait is asked to perform the OLS. What is the best course of action?
- Administer the test and disregard the injury
- Do not use OLS; rely on other validated tests or observations (Correct answer)
- Use only the first 15 seconds of the test
- Allow the subject to choose which leg to raise
Correct answer: Do not use OLS; rely on other validated tests or observations
Physical impairments that affect balance, such as leg injuries, can invalidate OLS results; officers should note the condition and use alternative assessments.
Question 3: During OLS, the officer times the subject for 30 seconds. When should the officer tell the subject to stop?
- After the subject says 'one-thousand-thirty'
- When the officer's 30-second stopwatch expires (Correct answer)
- When the subject shows 2 or more clues
- After exactly 25 seconds to allow a safety margin
Correct answer: When the officer's 30-second stopwatch expires
The officer controls the 30-second duration using a stopwatch and instructs the subject to stop when the time is reached, regardless of the subject's counting.
Question 4: Two OLS clues are generally considered the threshold for indicating impairment. What percentage of impaired drivers (BAC ≥ 0.10) show two or more clues according to NHTSA research?
- 45%
- 63%
- 83% (Correct answer)
- 97%
Correct answer: 83%
NHTSA research found that 83% of subjects with a BAC of 0.10 or greater exhibited two or more OLS clues.
Question 5: During the OLS instruction phase, the officer tells the subject to keep arms at their sides. Why is this instruction critical?
- It prevents the subject from grabbing the officer
- It establishes a baseline behavior so any deviation can be scored as a clue (Correct answer)
- It is required by state law in all 50 states
- It prevents contamination of the HGN test
Correct answer: It establishes a baseline behavior so any deviation can be scored as a clue
Instructing the subject to keep arms at their sides sets the behavioral baseline so that raising arms beyond 6 inches can be identified and scored as a clue.
Question 6: A subject sways in a circular motion during OLS. How should the officer record this?
- Swaying — one clue (Correct answer)
- Swaying and hopping — two clues
- No clue; only side-to-side sway counts
- Loss of balance — record as a separate fifth clue
Correct answer: Swaying — one clue
Any observable body sway, regardless of direction, constitutes the single 'swaying while balancing' clue.
Question 7: When administering the OLS, where should the subject stand in relation to the officer?
- Behind the officer
- On level, hard, dry, non-slippery surface in front of the officer (Correct answer)
- At least 10 feet away to allow observation
- Adjacent to the patrol vehicle
Correct answer: On level, hard, dry, non-slippery surface in front of the officer
NHTSA requires the OLS to be performed on a level, hard, dry, non-slippery surface so that the environment does not unfairly affect balance.
SFST One Leg Stand 3
What counting method is the subject instructed to use during the OLS test?