The NHTSA Standardized Field Sobriety Testing (SFST) certification program trains law enforcement officers to detect alcohol-impaired drivers through a validated battery of three roadside tests. SFST certification is required in most states before officers can administer field sobriety tests and testify as experts in DUI prosecutions.
Our free SFST practice test PDF provides printable exam-style questions covering all three validated tests, clue administration, scoring criteria, and legal admissibility standards. Download it, print it out, and use it to reinforce your classroom training before your certification evaluation.
HGN is considered the most reliable of the three SFST tests, with a stand-alone accuracy rate of approximately 88% when properly administered. Nystagmus is the involuntary jerking of the eye, and alcohol consumption at or above the 0.08% BAC threshold significantly exaggerates this response. Officers administer HGN by having the subject follow a stimulus (pen, finger, or light) horizontally with their eyes while the officer checks for three clues in each eye: lack of smooth pursuit, distinct and sustained nystagmus at maximum deviation, and onset of nystagmus prior to 45 degrees. With six possible clues total, a score of four or more clues correlates with a BAC at or above 0.08% in approximately 88% of subjects.
The Walk-and-Turn is a divided attention test requiring the subject to simultaneously listen to instructions, maintain a physical position, and execute a walking task. The subject takes nine heel-to-toe steps along a real or imaginary line, turns in a prescribed manner, and returns nine steps. Officers score eight possible clues: cannot keep balance during instructions, starts before instructions are finished, stops while walking, does not touch heel-to-toe, steps off the line, uses arms for balance, makes an improper turn, and takes the wrong number of steps. Two or more clues indicate a BAC at or above 0.08% in approximately 79% of cases.
The One-Leg Stand requires the subject to stand on one foot while raising the other foot approximately six inches from the ground, toes pointed out, and count aloud (one-thousand-one, one-thousand-two, etc.) until told to stop. The test lasts 30 seconds. Officers score four possible clues: swaying while balancing, using arms for balance, hopping to maintain balance, and putting the foot down. Two or more clues indicate a BAC at or above 0.08% in approximately 83% of cases. Subjects with leg injuries, certain medical conditions, or who are more than 50 pounds overweight may perform poorly on OLS for non-alcohol-related reasons — officers must note any such conditions.
NHTSA's validation research was conducted under specific conditions, and the reliability figures only apply when those conditions are replicated in the field. Officers must administer SFST tests on a reasonably dry, hard, level, non-slippery surface with adequate lighting. The subject must not be wearing footwear that interferes with balance (heels higher than two inches may be removed). Officers must give the exact standardized instructions verbatim and demonstrate each test as specified. Deviations from standardized procedure can — and frequently do — provide defense attorneys grounds to challenge or exclude SFST results in court.
One common misconception is that SFST results directly measure BAC. They do not. SFST is a probabilistic screening tool — officers observe behavioral clues and correlate their count with the likelihood that a driver's BAC meets or exceeds the legal limit. The three-test battery combined has a validated accuracy rate of approximately 91% when all tests are properly administered and scored. The results inform the officer's decision to make an arrest; they do not replace a chemical test (breath, blood, or urine) for evidentiary purposes.
SFST was designed primarily to detect alcohol impairment, but officers frequently encounter drivers impaired by drugs other than alcohol. The Drug Recognition Expert (DRE) program, also NHTSA-endorsed, extends field impairment detection to seven drug categories. HGN remains relevant in the DRE protocol because certain drug categories (CNS depressants, dissociative anesthetics) also cause nystagmus, while stimulants and cannabis do not. SFST practitioners should understand the limitations of the battery with drug-impaired subjects and know when to request a DRE evaluation.
SFST evidence has been challenged under both Frye and Daubert standards in courts across the country. The prevailing judicial consensus holds that properly administered SFST results are admissible as lay opinion evidence (the officer's observed clues) or, for certified instructors, as expert opinion. Officers must be able to articulate that they received NHTSA-certified SFST training, that they administered the tests according to the standardized protocol, and that their clue observations are consistent with NHTSA's documented indicators. Documentation quality directly affects prosecutorial outcomes — every clue observed must be recorded in the officer's notes at the time of the stop, not reconstructed later from memory.
SFST Practitioner certification is the baseline credential, typically completed in a 16-hour course combining classroom instruction and wet lab practice with live volunteer subjects at or above the legal BAC limit. Practitioners can administer SFST in the field and testify about their observations. SFST Instructors complete an additional 24-hour advanced course and must be certified by a state-level SFST coordinator. Instructors can train and certify new practitioners and may carry greater weight as expert witnesses. Both certifications require periodic recertification to maintain current status.
Reinforce your certification prep with our full interactive SFST practice test online. Get instant feedback on each question, review answer explanations tied to NHTSA guidelines, and track your progress across the HGN, WAT, and OLS domains before your certification evaluation.