SFST EXAM & PRACTICE TEST BANK
2026/2027 — STANDARDIZED FIELD
SOBRIETY TESTING COMPLETE
STUDY GUIDE WITH 300 REAL EXAM
QUESTIONS, VERIFIED ANSWERS &
DETAILED RATIONALES
Section 1: Horizontal Gaze Nystagmus (HGN) Test
1. What does HGN stand for?
A. Horizontal Gaze Nystagmus
B. Horizontal Gaze Neurological
C. Head Gaze Nystagmus
D. Horizontal Gaze Normal
Correct Answer: A. Horizontal Gaze Nystagmus.
Rationale: HGN is the involuntary jerking of the eyes as they gaze toward the side. It is
the first test administered in the SFST battery.
2. What is resting nystagmus?
A. Jerking of the eyes as they look straight ahead
B. Jerking of the eyes looking upward
C. Jerking of the eyes looking to the side
D. Jerking of the eyes when closing
Correct Answer: A. Jerking of the eyes as they look straight ahead.
Rationale: Resting nystagmus is observed when the eyes are in a neutral position. It
usually indicates a pathological disorder or high doses of a dissociative anesthetic drug
such as PCP.
3. What is vertical gaze nystagmus?
A. Involuntary jerking of the eyes looking upward at maximum elevation
B. Involuntary jerking of the eyes looking downward
C. Jerking of the eyes as they look straight ahead
D. Jerking of the eyes during smooth pursuit
,Correct Answer: A. Involuntary jerking of the eyes looking upward at maximum
elevation.
Rationale: Vertical gaze nystagmus is checked after HGN and may indicate
impairment. It must be definite, distinct, and sustained for a minimum of 4 seconds to
be recorded.
4. What is horizontal gaze nystagmus?
A. Involuntary jerking of the eyes as they gaze toward the side
B. Involuntary jerking of the eyes looking upward
C. Jerking of the eyes looking straight ahead
D. Jerking of the eyes when blinking
Correct Answer: A. Involuntary jerking of the eyes as they gaze toward the side.
Rationale: HGN is the most reliable indicator of alcohol impairment. As BAC increases,
the angle of onset of nystagmus decreases from 45 degrees toward the center.
5. How many validated clues have been established for the HGN test?
A. 3
B. 4
C. 6
D. 8
Correct Answer: C. 6.
Rationale: There are 3 clues per eye, for a total of 6 validated clues. The clues are: lack
of smooth pursuit, distinct and sustained nystagmus at maximum deviation, and onset
of nystagmus prior to 45 degrees.
6. What is the maximum number of clues for HGN that can appear in one eye?
A. 1
B. 2
C. 3
D. 4
Correct Answer: C. 3.
Rationale: Each eye can exhibit up to 3 validated clues. The maximum total across both
eyes is 6.
7. If resting nystagmus is observed with a subject, this may be an indicator of:
A. Alcohol impairment
B. A medical condition
C. Drug impairment
D. Fatigue
Correct Answer: B. A medical condition.
Rationale: Resting nystagmus is not a validated clue for alcohol impairment. It typically
,indicates a pathological disorder or high doses of a dissociative anesthetic drug such as
PCP.
8. When checking for lack of smooth pursuit, the stimulus should be moved at
approximately how many seconds from center to side?
A. 1 second
B. 2 seconds
C. 3 seconds
D. 4 seconds
Correct Answer: B. 2 seconds.
Rationale: The stimulus should be moved smoothly at a speed that requires
approximately 2 seconds to bring the eye as far to the side as it can go.
9. The recommended position of the stimulus for checking HGN is
approximately how far from the subject's nose?
A. 6-8 inches
B. 12-15 inches
C. 18-20 inches
D. 24 inches
Correct Answer: B. 12-15 inches.
Rationale: The stimulus should be positioned about 12-15 inches from the subject's
nose and slightly above eye level.
10. What are the three checks of the eyes done prior to the administration of
HGN to assess possible medical impairment?
A. Equal pupil size, resting nystagmus, and equal tracking
B. Visual acuity, color vision, and peripheral vision
C. Eye pressure, tear production, and blink rate
D. Pupil dilation, eye movement, and focus
Correct Answer: A. Equal pupil size, resting nystagmus, and equal tracking.
Rationale: These three checks help identify medical conditions or injuries that could
affect the validity of the HGN test.
11. What is the second clue of the HGN test?
A. Lack of smooth pursuit
B. Distinct and sustained nystagmus at maximum deviation
C. Onset of nystagmus prior to 45 degrees
D. Resting nystagmus
Correct Answer: B. Distinct and sustained nystagmus at maximum deviation.
Rationale: The clues in order are: (1) Lack of smooth pursuit, (2) Distinct and sustained
nystagmus at maximum deviation, (3) Onset of nystagmus prior to 45 degrees.
, 12. When checking for the onset of nystagmus prior to 45 degrees, the stimulus
should be moved at a speed from center in approximately how many seconds
to reach a 45-degree angle?
A. 1 second
B. 2 seconds
C. A minimum of 4 seconds
D. 6 seconds
Correct Answer: C. A minimum of 4 seconds.
Rationale: The stimulus should be moved slowly—taking at least 4 seconds to reach the
45-degree angle—to allow the officer to observe the onset of nystagmus.
13. When checking for the onset of nystagmus prior to 45 degrees, once you
see the jerking begin, you should immediately stop moving the stimulus and
hold it steady to:
A. Verify that the jerking is continuing
B. Allow the subject to rest
C. Check for equal tracking
D. Measure the angle
Correct Answer: A. Verify that the jerking is continuing.
Rationale: Holding the stimulus steady allows the officer to confirm that the nystagmus
is distinct and sustained, rather than a random eye movement.
14. Equal tracking is defined as:
A. Both eyes showing the same number of clues
B. The eyes moving together smoothly and symmetrically
C. The stimulus being held at the same distance from both eyes
D. Checking each eye separately
Correct Answer: B. The eyes moving together smoothly and symmetrically.
Rationale: Equal tracking is a preliminary check to ensure both eyes can smoothly and
simultaneously follow the stimulus. If they cannot, there may be a medical or
neurological issue.
15. If a subject's eyes do not track together, what should the officer do?
A. Discontinue the test
B. Ask if they have a medical condition or injury
C. Proceed with the test anyway
D. Arrest the subject immediately
Correct Answer: B. Ask if they have a medical condition or injury.
Rationale: Unequal tracking could indicate a medical condition, injury, or visual
impairment that may affect nystagmus observed. The officer should inquire about this
before proceeding.
2026/2027 — STANDARDIZED FIELD
SOBRIETY TESTING COMPLETE
STUDY GUIDE WITH 300 REAL EXAM
QUESTIONS, VERIFIED ANSWERS &
DETAILED RATIONALES
Section 1: Horizontal Gaze Nystagmus (HGN) Test
1. What does HGN stand for?
A. Horizontal Gaze Nystagmus
B. Horizontal Gaze Neurological
C. Head Gaze Nystagmus
D. Horizontal Gaze Normal
Correct Answer: A. Horizontal Gaze Nystagmus.
Rationale: HGN is the involuntary jerking of the eyes as they gaze toward the side. It is
the first test administered in the SFST battery.
2. What is resting nystagmus?
A. Jerking of the eyes as they look straight ahead
B. Jerking of the eyes looking upward
C. Jerking of the eyes looking to the side
D. Jerking of the eyes when closing
Correct Answer: A. Jerking of the eyes as they look straight ahead.
Rationale: Resting nystagmus is observed when the eyes are in a neutral position. It
usually indicates a pathological disorder or high doses of a dissociative anesthetic drug
such as PCP.
3. What is vertical gaze nystagmus?
A. Involuntary jerking of the eyes looking upward at maximum elevation
B. Involuntary jerking of the eyes looking downward
C. Jerking of the eyes as they look straight ahead
D. Jerking of the eyes during smooth pursuit
,Correct Answer: A. Involuntary jerking of the eyes looking upward at maximum
elevation.
Rationale: Vertical gaze nystagmus is checked after HGN and may indicate
impairment. It must be definite, distinct, and sustained for a minimum of 4 seconds to
be recorded.
4. What is horizontal gaze nystagmus?
A. Involuntary jerking of the eyes as they gaze toward the side
B. Involuntary jerking of the eyes looking upward
C. Jerking of the eyes looking straight ahead
D. Jerking of the eyes when blinking
Correct Answer: A. Involuntary jerking of the eyes as they gaze toward the side.
Rationale: HGN is the most reliable indicator of alcohol impairment. As BAC increases,
the angle of onset of nystagmus decreases from 45 degrees toward the center.
5. How many validated clues have been established for the HGN test?
A. 3
B. 4
C. 6
D. 8
Correct Answer: C. 6.
Rationale: There are 3 clues per eye, for a total of 6 validated clues. The clues are: lack
of smooth pursuit, distinct and sustained nystagmus at maximum deviation, and onset
of nystagmus prior to 45 degrees.
6. What is the maximum number of clues for HGN that can appear in one eye?
A. 1
B. 2
C. 3
D. 4
Correct Answer: C. 3.
Rationale: Each eye can exhibit up to 3 validated clues. The maximum total across both
eyes is 6.
7. If resting nystagmus is observed with a subject, this may be an indicator of:
A. Alcohol impairment
B. A medical condition
C. Drug impairment
D. Fatigue
Correct Answer: B. A medical condition.
Rationale: Resting nystagmus is not a validated clue for alcohol impairment. It typically
,indicates a pathological disorder or high doses of a dissociative anesthetic drug such as
PCP.
8. When checking for lack of smooth pursuit, the stimulus should be moved at
approximately how many seconds from center to side?
A. 1 second
B. 2 seconds
C. 3 seconds
D. 4 seconds
Correct Answer: B. 2 seconds.
Rationale: The stimulus should be moved smoothly at a speed that requires
approximately 2 seconds to bring the eye as far to the side as it can go.
9. The recommended position of the stimulus for checking HGN is
approximately how far from the subject's nose?
A. 6-8 inches
B. 12-15 inches
C. 18-20 inches
D. 24 inches
Correct Answer: B. 12-15 inches.
Rationale: The stimulus should be positioned about 12-15 inches from the subject's
nose and slightly above eye level.
10. What are the three checks of the eyes done prior to the administration of
HGN to assess possible medical impairment?
A. Equal pupil size, resting nystagmus, and equal tracking
B. Visual acuity, color vision, and peripheral vision
C. Eye pressure, tear production, and blink rate
D. Pupil dilation, eye movement, and focus
Correct Answer: A. Equal pupil size, resting nystagmus, and equal tracking.
Rationale: These three checks help identify medical conditions or injuries that could
affect the validity of the HGN test.
11. What is the second clue of the HGN test?
A. Lack of smooth pursuit
B. Distinct and sustained nystagmus at maximum deviation
C. Onset of nystagmus prior to 45 degrees
D. Resting nystagmus
Correct Answer: B. Distinct and sustained nystagmus at maximum deviation.
Rationale: The clues in order are: (1) Lack of smooth pursuit, (2) Distinct and sustained
nystagmus at maximum deviation, (3) Onset of nystagmus prior to 45 degrees.
, 12. When checking for the onset of nystagmus prior to 45 degrees, the stimulus
should be moved at a speed from center in approximately how many seconds
to reach a 45-degree angle?
A. 1 second
B. 2 seconds
C. A minimum of 4 seconds
D. 6 seconds
Correct Answer: C. A minimum of 4 seconds.
Rationale: The stimulus should be moved slowly—taking at least 4 seconds to reach the
45-degree angle—to allow the officer to observe the onset of nystagmus.
13. When checking for the onset of nystagmus prior to 45 degrees, once you
see the jerking begin, you should immediately stop moving the stimulus and
hold it steady to:
A. Verify that the jerking is continuing
B. Allow the subject to rest
C. Check for equal tracking
D. Measure the angle
Correct Answer: A. Verify that the jerking is continuing.
Rationale: Holding the stimulus steady allows the officer to confirm that the nystagmus
is distinct and sustained, rather than a random eye movement.
14. Equal tracking is defined as:
A. Both eyes showing the same number of clues
B. The eyes moving together smoothly and symmetrically
C. The stimulus being held at the same distance from both eyes
D. Checking each eye separately
Correct Answer: B. The eyes moving together smoothly and symmetrically.
Rationale: Equal tracking is a preliminary check to ensure both eyes can smoothly and
simultaneously follow the stimulus. If they cannot, there may be a medical or
neurological issue.
15. If a subject's eyes do not track together, what should the officer do?
A. Discontinue the test
B. Ask if they have a medical condition or injury
C. Proceed with the test anyway
D. Arrest the subject immediately
Correct Answer: B. Ask if they have a medical condition or injury.
Rationale: Unequal tracking could indicate a medical condition, injury, or visual
impairment that may affect nystagmus observed. The officer should inquire about this
before proceeding.
