Standardized Field Sobriety Test Clues — How SFSTs Work and What Officers Look For

If you’ve ever been pulled over on suspicion of driving under the influence, or simply watched a roadside evaluation unfold, you may have wondered exactly what the officer is assessing. The Standardized Field Sobriety Test is a precise, structured process — not a gut-feeling judgment call. Each test comes with scripted instructions and a defined set of behavioral clues that trained officers are expected to identify and document. This guide walks through every component, from the HGN test steps to the walk and turn sequence to how results are recorded on an SFST score sheet. All details here are drawn directly from the Standardized Field Sobriety Testing Manual used in drug and alcohol detection training.

What Is a Standard Field Sobriety Test?

A Standard Field Sobriety Test is a roadside evaluation that law enforcement officers perform to observe physical and cognitive signs of impairment during a traffic stop. These aren’t arbitrary exercises — each test is built around well-documented behavioral patterns that correlate with alcohol or drug impairment.

Three core SFSTs have been nationally validated and are administered under guidelines developed with support from the National Highway Traffic Safety Administration. The NHTSA SFST manual defines exactly how each test should be given, what qualifies as a clue, and how evaluations should be documented. Officers follow these SFST instructions precisely so that results are consistent and defensible.

The three nationally standardized tests are:

Horizontal Gaze Nystagmus (HGN)
Walk and Turn (WAT)
One-Leg Stand (OLS)

Horizontal Gaze Nystagmus: Steps and Clues

The HGN test is typically administered first. It checks for involuntary jerking of the eyes — a physiological response that intensifies when a person is impaired by alcohol or certain substances. The officer uses a small stimulus, such as a pen or finger, and moves it slowly across the subject’s visual field while watching how the eyes track it.

HGN Test Steps

The official HGN test steps, delivered to the subject during the evaluation, are:

“I am going to check your eyes. Please remove your glasses.”
“Keep your head still and follow the stimulus with your eyes only.”
“Do not move your head.”
“Do you understand the instructions?”

Horizontal Gaze Nystagmus Clues

There are six HGN clues in total — three assessed for each eye. These horizontal gaze nystagmus clues are what make the HGN test the most clinically grounded of the three evaluations:

Lack of smooth pursuit — the eye jerks or bounces rather than gliding smoothly while following the stimulus
Distinct nystagmus at maximum deviation — the eye twitches visibly when held at its farthest lateral position
Onset of nystagmus prior to 45 degrees — the jerking begins before the eye reaches a 45-degree angle from center

Each of these HGN test clues is assessed separately for the left and right eye, producing a maximum possible score of six. The official instructions note that there are no specific clues assigned to vertical nystagmus — that is a separate and distinct phenomenon. Whether you’re reviewing this as an HGN cheat sheet for training or trying to understand what an officer observed, these three indicators are the foundation of the entire HGN evaluation.

Walk and Turn: Instructions and Clues

The Walk and Turn test is a divided-attention exercise. It requires the subject to listen carefully to a series of instructions while simultaneously preparing to perform a physical task — a deliberate design choice, since impairment affects both attention and motor coordination at once.

Walk and Turn Instructions

Put your left foot on the line and right foot in front with the right heel touching the left toe. Keep hands at sides.
Do not start until told to do so.
Do you understand the directions?
When told to begin, take nine heel-to-toe steps on the line, turn keeping one foot on the line, and return with nine more heel-to-toe steps.
On the ninth step, keep the front foot on the line and turn by taking several small steps with the other foot.
While walking, watch your feet at all times, keep arms at your sides, and count your steps out loud.
Once you begin, do not stop until the test is completed.
You may begin the test.

Walk and Turn Clues

The SFST walk and turn clues are split across two phases, with eight total indicators the officer watches for:

Instruction Phase — 2 clues:

Cannot keep balance while listening to instructions
Starts walking before being told to begin

Walking Phase — 6 clues:

Stops while walking
Misses heel to toe
Steps off the line
Uses arms to balance
Makes an improper turn
Takes the wrong number of steps

One-Leg Stand: Instructions and Clues

Like the Walk and Turn, the One-Leg Stand is a divided-attention test. It pairs a sustained balance requirement with a counting task — assessing whether the subject can manage both physical control and cognitive focus simultaneously.

One-Leg Stand Instructions

Stand with your heels together and arms at your sides.
Do not begin until told to.
Do you understand?
When told to, raise one leg — either leg — approximately six inches off the ground with the foot pointed out.
Keep both legs straight and keep your eyes on the elevated foot.
While holding that position, count aloud: “one thousand and one, one thousand and two, one thousand and three…” until told to stop.
You may begin the test.

One-Leg Stand Test Clues

There are four One-Leg Stand test clues the officer records:

Swaying while balancing
Using arms to balance
Hopping
Putting the foot down

All Standardized Field Sobriety Test Clues at a Glance

If you want a quick Standard Field Sobriety Test cheat sheet comparing all three tests in one place, the table below covers every category of Standardized Field Sobriety Test clues across all three SFSTs. It’s useful whether you’re studying for a law enforcement exam, preparing for court, or simply reviewing an evaluation after the fact.

Test	Total Clues	Phase Breakdown	Key Indicators
Horizontal Gaze Nystagmus (HGN)	6 (3 per eye)	Single phase	Smooth pursuit; max deviation; 45° onset
Walk and Turn (WAT)	8	2 instruction + 6 walking	Balance, timing, heel-to-toe, line contact, arms, turn, step count
One-Leg Stand (OLS)	4	Single phase	Swaying, arm use, hopping, foot down

This SFST cheat sheet overview is a useful reference, but it’s important to remember that each clue is only meaningful when officers administer the tests correctly and consistently — exactly as outlined in the NHTSA DUI manual.

Additional Field Sobriety Tests Beyond the Core Three

Beyond the three nationally validated SFSTs, officers may incorporate supplemental evaluations as part of a broader roadside assessment. These are not part of the core NHTSA-standardized battery, but they appear in field sobriety training materials:

Romberg Balance Test: The subject stands with feet together, arms at sides, head tilted back, and eyes closed. They are asked to estimate when 30 seconds have passed. This evaluates both physical balance and time perception — two abilities commonly disrupted by impairment.
Finger-to-Nose Test: The subject stands with heels and toes together, arms at sides, head tilted back, and eyes closed. They then alternate touching the tip of their nose with each index finger. This assesses fine motor coordination and balance simultaneously.

The Drug Recognition Expert (DRE) Process

When drug impairment — beyond or in place of alcohol — is suspected, specially trained Drug Recognition Experts follow a broader 12-step protocol. This process goes well beyond the standard SFST battery and incorporates physiological measurements alongside behavioral observation:

Breath test
Interview of the arresting officer
Preliminary examination (first pulse check)
Eye examination
Divided attention psychophysical tests
Vital signs check (second pulse measurement)
Dark room examination
Muscle tone check
Check for injection sites (third pulse measurement)
Interrogation
Opinion of the evaluator
Toxicological examination

Three separate pulse measurements are taken at different stages of this evaluation — an important structural detail that distinguishes it from the simpler roadside SFST battery.

Normal Physiological Ranges Used in Assessments

During a DRE evaluation, the officer compares the subject’s vital signs against established baselines. Values outside these normal ranges may indicate impairment by specific categories of substances:

Measurement	Normal Range
Pulse	60–90 BPM
Pupil Size	3.0–6.5 mm
Blood Pressure (Systolic)	120–140 mm/Hg
Blood Pressure (Diastolic)	70–90 mm/Hg
Body Temperature	98.6°F (±1°)

How Officers Identify Potentially Impaired Drivers Before the Stop

Law enforcement observation doesn’t always begin at the moment a vehicle is pulled over. Officers are trained to recognize driving behaviors that may suggest impairment while vehicles are still in motion. These observations fall into four broad categories:

Problems maintaining proper lane position
Speed and braking problems
Vigilance problems — difficulty staying focused on the driving task
Judgment problems — taking unnecessary risks or endangering other road users

These pre-stop observations typically appear in the officer’s written report and can play a role in how the overall stop is documented and interpreted.

How SFST Scoring Works in Practice

When an officer completes the evaluation, each observed behavior is noted on the SFST score sheet. The clue system is designed so that a minimum number of indicators — rather than a single observation — carries evidentiary weight. Two or more clues on the One-Leg Stand, or two or more on the Walk and Turn, are considered significant findings. On the HGN evaluation, four or more clues out of a possible six is the common threshold that indicates probable impairment.

The SFST clues system isn’t a strict pass/fail mechanism — it’s a structured observation tool. What matters is that the evaluation is administered correctly each time. That’s precisely why the protocol in the Standardized Field Sobriety Testing Manual exists: to make the process consistent, reproducible, and fair regardless of which officer is conducting the stop.

Conclusion

The Standardized Field Sobriety Test system is far more structured than most people realize. Every instruction is scripted. Every clue is defined before the officer ever approaches a vehicle. The HGN test’s six horizontal gaze nystagmus clues, the Walk and Turn’s eight behavioral indicators split across two phases, and the One-Leg Stand’s four observable signs form a reproducible evaluation framework that trained officers apply consistently. When additional evaluation is needed, the 12-step DRE protocol adds physiological measurements and a more comprehensive picture of potential drug impairment.

Understanding how SFST instructions are structured — what each test involves, which behaviors count as clues, and how documentation works — gives drivers, legal professionals, and trainees alike a much clearer view of what happens during a DUI evaluation and why the process is designed the way it is.