SFST HGN Test 2 — Questions and Answers
Question 1: During HGN testing, at what angle from center should the officer begin checking for Lack of Smooth Pursuit?
- 10 degrees
- 20 degrees (Correct answer)
- 45 degrees
- Directly at center
Correct answer: 20 degrees
The officer begins moving the stimulus from center and checks for Lack of Smooth Pursuit as the eye tracks through the full range of motion.
Question 2: Which medical condition can produce HGN clues that may be mistaken for alcohol impairment?
- Type 2 diabetes
- Inner ear disorder (labyrinthitis) (Correct answer)
- Hypertension
- Asthma
Correct answer: Inner ear disorder (labyrinthitis)
Inner ear disorders such as labyrinthitis can cause nystagmus that mimics alcohol-induced HGN, which officers must consider.
Question 3: In the HGN test, how many total clues is the officer looking for across both eyes?
- 3
- 4
- 6 (Correct answer)
- 8
Correct answer: 6
Officers check for three clues in each eye (Lack of Smooth Pursuit, Distinct Nystagmus at Maximum Deviation, and Onset of Nystagmus Prior to 45 Degrees), totaling six clues.
Question 4: What does 'Distinct and Sustained Nystagmus at Maximum Deviation' mean in the HGN test?
- The eye jerks while smoothly tracking
- The eye jerks clearly and continuously when held at the far edge of gaze (Correct answer)
- The eye deviates beyond 45 degrees on its own
- The pupil dilates when held at maximum deviation
Correct answer: The eye jerks clearly and continuously when held at the far edge of gaze
At maximum deviation, the eye is held for at least four seconds and a clue is recorded if clear, sustained jerking is observed.
Question 5: A subject's eye onset of nystagmus is observed at 40 degrees. How should this clue be scored?
- Not a clue because it is past 45 degrees
- A clue because onset occurred before 45 degrees (Correct answer)
- Only a clue if both eyes show onset at 40 degrees
- Inconclusive — recheck at a different speed
Correct answer: A clue because onset occurred before 45 degrees
Onset of nystagmus prior to 45 degrees is a clue; 40 degrees is less than 45, so this eye earns that clue.
Question 6: Why must the HGN stimulus be held at maximum deviation for a minimum of four seconds?
- To allow the pupil to fully dilate
- To distinguish voluntary nystagmus from alcohol-induced nystagmus (Correct answer)
- To ensure the subject is not blinking excessively
- To allow the officer to estimate the angle of deviation
Correct answer: To distinguish voluntary nystagmus from alcohol-induced nystagmus
Holding for four seconds allows the officer to confirm that the nystagmus is distinct and sustained rather than a brief, voluntary eye movement.
Question 7: Which of the following is NOT a standardized HGN clue recognized by NHTSA?
- Lack of Smooth Pursuit
- Onset of Nystagmus Prior to 45 Degrees
- Vertical Nystagmus at Maximum Deviation (Correct answer)
- Distinct Nystagmus at Maximum Deviation
Correct answer: Vertical Nystagmus at Maximum Deviation
The three NHTSA HGN clues are Lack of Smooth Pursuit, Distinct Nystagmus at Maximum Deviation, and Onset Prior to 45 Degrees; Vertical Nystagmus is a separate check, not one of the three standard clues.
SFST HGN Test 2
During HGN testing, at what angle from center should the officer begin checking for Lack of Smooth Pursuit?