SFST Evaluation Factors 2 — Questions and Answers
Question 1: During the Walk-and-Turn test, which clue involves the suspect failing to maintain heel-to-toe contact by more than half an inch?
- Misses heel-to-toe (Correct answer)
- Steps off line
- Raises arms for balance
- Stops while walking
Correct answer: Misses heel-to-toe
Missing heel-to-toe contact by more than half an inch is one of the eight scored clues on the Walk-and-Turn test.
Question 2: When administering the HGN test, how many passes should the officer make during the check for distinct and sustained nystagmus at maximum deviation?
- Two passes, holding each eye at maximum deviation for at least 4 seconds (Correct answer)
- One pass across both eyes simultaneously
- Three rapid passes without holding
- Four passes, two seconds each
Correct answer: Two passes, holding each eye at maximum deviation for at least 4 seconds
The officer makes two passes, holding the stimulus at maximum deviation for a minimum of 4 seconds per eye to check for sustained nystagmus.
Question 3: A suspect with a prosthetic leg requests to perform the One-Leg Stand. What is the officer's recommended course of action?
- Administer an alternative non-balance test (Correct answer)
- Proceed with the test and note the prosthesis in the report
- Skip all SFSTs and proceed directly to arrest
- Allow the test only if the prosthesis is on the non-raised leg
Correct answer: Administer an alternative non-balance test
Suspects with prosthetic legs should not perform balance-based tests; officers should use alternative methods or document the limitation.
Question 4: Which factor can cause a false positive for Vertical Gaze Nystagmus (VGN) unrelated to drug impairment?
- High doses of depressants or dissociative anesthetics only produce VGN (Correct answer)
- VGN can appear in anyone under bright lighting conditions
- Caffeine consumption routinely produces VGN
- VGN is always present regardless of substance use
Correct answer: High doses of depressants or dissociative anesthetics only produce VGN
VGN is typically associated with high blood alcohol concentration or certain drug categories like dissociative anesthetics, not common environmental factors.
Question 5: On the One-Leg Stand, the clue 'puts foot down' is scored when the suspect:
- Lowers the raised foot to the ground before the officer says to stop (Correct answer)
- Switches which foot is raised during the test
- Hops more than once on the standing foot
- Counts faster than instructed
Correct answer: Lowers the raised foot to the ground before the officer says to stop
Putting the foot down before being told to stop is a distinct scored clue on the One-Leg Stand test.
Question 6: Which environmental condition most significantly affects the reliability of the Walk-and-Turn test?
- An uneven or sloped surface (Correct answer)
- Daytime versus nighttime administration
- The suspect's clothing type
- Wind speed above 10 mph
Correct answer: An uneven or sloped surface
NHTSA requires a reasonably dry, hard, level, non-slippery surface; uneven or sloped surfaces compromise test validity.
Question 7: During HGN evaluation, 'lack of smooth pursuit' is defined as the eye:
- Jerking or bouncing as it follows the stimulus (Correct answer)
- Failing to track the stimulus at all
- Moving only in a vertical direction
- Dilating in response to the stimulus movement
Correct answer: Jerking or bouncing as it follows the stimulus
Lack of smooth pursuit occurs when the eye jerks or bounces rather than tracking smoothly as it follows the moving stimulus.
SFST Evaluation Factors 2
During the Walk-and-Turn test, which clue involves the suspect failing to maintain heel-to-toe contact by more than half an inch?