SFST HGN Test 3 — Questions and Answers
Question 1: When administering the HGN test, the officer should position the stimulus how far in front of and above the subject's eyes?
- 6–8 inches in front, slightly above eye level (Correct answer)
- 12–15 inches in front, at eye level
- 18–20 inches in front, above eye level
- 3–4 inches in front, at nose level
Correct answer: 6–8 inches in front, slightly above eye level
NHTSA guidelines specify holding the stimulus 6–8 inches from the subject's nose and slightly above eye level to keep the eyes in a natural position.
Question 2: Which of the following correctly describes the recommended speed for moving the stimulus during the Lack of Smooth Pursuit check?
- As fast as possible to catch jerking motion
- Approximately two seconds from center to the edge of each eye
- One full sweep (left to right) in one second
- Four seconds from center to the edge of each eye (Correct answer)
Correct answer: Four seconds from center to the edge of each eye
NHTSA instructs the officer to take approximately four seconds to move the stimulus from center to the maximum deviation of each eye during the smooth pursuit check.
Question 3: Vertical Gaze Nystagmus (VGN) during the HGN test is associated with which condition?
- Low blood alcohol concentration (BAC below 0.05)
- High BAC or influence of certain depressants (Correct answer)
- Cannabis intoxication
- Stimulant use only
Correct answer: High BAC or influence of certain depressants
VGN typically appears at higher BAC levels or with depressant drugs, making it an indicator of significant impairment.
Question 4: A subject wears contact lenses during the HGN test. What should the officer do?
- Require the subject to remove them before testing
- Note that contacts are present but continue the test normally (Correct answer)
- Discontinue HGN and rely only on WAT and OLS
- Administer an eye-drop check first
Correct answer: Note that contacts are present but continue the test normally
Contact lenses do not affect the validity of the HGN test; the officer notes their presence in the report and proceeds normally.
Question 5: An officer observes 4 out of 6 HGN clues. According to NHTSA research, this result suggests:
- The subject is likely below 0.08 BAC
- There is a high probability the subject's BAC is 0.08 or above (Correct answer)
- The test is inconclusive and should be repeated
- Only two clues are needed for a DUI arrest
Correct answer: There is a high probability the subject's BAC is 0.08 or above
NHTSA research indicates that four or more HGN clues correlate with a BAC of 0.08 or higher with approximately 88% accuracy.
Question 6: Which phrase best describes 'Lack of Smooth Pursuit' as an HGN clue?
- The eye remains stationary instead of following the stimulus
- The eye moves jerkily rather than gliding smoothly as it tracks the stimulus (Correct answer)
- The eye moves faster than the stimulus
- The pupil changes size while tracking the stimulus
Correct answer: The eye moves jerkily rather than gliding smoothly as it tracks the stimulus
Lack of Smooth Pursuit is observed when the eye shows visible jerking or bouncing motion instead of smoothly following the moving stimulus.
Question 7: How should an officer handle a subject who cannot keep their head still during the HGN test?
- Manually hold the subject's head in place
- Ask the subject to hold their head still and restart if movement continues (Correct answer)
- Administer the test without modification and note the movement
- Skip HGN and proceed directly to arrest
Correct answer: Ask the subject to hold their head still and restart if movement continues
The officer should instruct the subject to keep their head still; if movement continues it should be documented, as it may invalidate clue observations.
SFST HGN Test 3
When administering the HGN test, the officer should position the stimulus how far in front of and above the subject's eyes?