If you’ve been pulled over for suspected DUI, a police officer may ask you to do “roadside tests” like walking a line or standing on one leg. These are commonly called Field Sobriety Tests (FSTs). The standardized versions are often called SFSTs (Standardized Field Sobriety Tests).
These tests can feel like a pass/fail exam—but in real DUI cases, they’re not a clean measure of impairment. They’re a set of observations that can be influenced by nerves, fatigue, injuries, uneven pavement, lighting, footwear, and an officer’s interpretation.
This page and website provide general information in plain English, not legal advice. Laws and local court/DMV practices vary and can change, so don’t rely on this content for your case—talk to a qualified attorney promptly to review your specific facts, especially if you face charges, a DMV action, or a deadline. In many cases, you’re fighting two battles at once: the DMV process and the criminal court case.
What Are “SFSTs” (Standardized Field Sobriety Tests)?
Law enforcement commonly relies on a standard battery of SFSTs associated with NHTSA/IACP training. NHTSA refresher training materials identify the three SFSTs as HGN (Horizontal Gaze Nystagmus), Walk-and-Turn, and One-Leg Stand.
The key concept behind these tests is divided attention—asking someone to do a physical task while following instructions and maintaining balance/focus. NHTSA SFST training materials describe Walk-and-Turn and One-Leg Stand as “psychophysical” divided-attention tests.
This page and website provide general information in plain English, not legal advice. Laws and local court/DMV practices vary and can change, so don’t rely on this content for your case—talk to a qualified attorney promptly to review your specific facts, especially if you face charges, a DMV action, or a deadline. In many cases, you’re fighting two battles at once: the DMV process and the criminal court case.
The 3 Standardized Tests Officers Use Most
1) HGN (Horizontal Gaze Nystagmus)
This is the eye test where the officer moves a stimulus (often a pen) and watches for involuntary jerking in your eyes.
2) Walk-and-Turn (WAT)
This is the “heel-to-toe” line-walk test with a turn and a specific number of steps.
3) One-Leg Stand (OLS)
This is the test where you raise one foot and count while balancing.
NHTSA refresher materials explicitly teach that there are distinct “clues” for each test and training expects officers to know them (e.g., eight clues for Walk-and-Turn; four clues for One-Leg Stand).
HGN Test: What Officers Look For
How it’s commonly scored (in plain English)
A prosecutor may argue that HGN is “scientific” because it involves eye movement rather than balance. In training-oriented SFST resources, HGN is described as having six total clues (three in each eye).
One training reference also notes an inference tied to the number of clues observed (for example, 4+ clues suggesting .08+), while also pointing back to the NHTSA student manual.
Why HGN gets challenged
Even when officers are trained, defense lawyers often scrutinize:
•whether the officer followed correct steps and timing,
•whether lighting, stimulus distance, or distractions affected the observation,
•whether a medical/neurological condition could mimic nystagmus,
•whether the video matches the officer’s report.
Walk-and-Turn Test: Common “Clues”
Walk-and-Turn includes two phases: an instruction phase (standing in position while listening) and a walking phase.
A widely used SFST scoring sheet lists the classic Walk-and-Turn “clues,” including items such as:
•can’t balance during instructions
•starts too soon
•stops while walking
•misses heel-to-toe
•steps off the line
•uses arms to balance
•turns improperly
•wrong number of steps
NHTSA refresher materials also teach that Walk-and-Turn has eight distinct clues.
Why Walk-and-Turn is vulnerable
Walk-and-Turn can look “bad” for reasons that have nothing to do with alcohol:
•uneven pavement, gravel, slope, cracks, wet surfaces
•poor lighting (common on SoCal roads at night)
•boots, dress shoes, sandals
•age, injuries, inner-ear issues, or general balance problems
•anxiety (many sober people perform awkwardly when being evaluated)
One-Leg Stand Test: Common “Clues”
One-Leg Stand is another divided-attention test (balance + counting).
NHTSA refresher materials teach that One-Leg Stand has four distinct clues.
SFST scoring sheets commonly list clues such as:
•sways while balancing
•uses arms to balance
•hopping
•puts foot down
Why One-Leg Stand is vulnerable
Balancing on one foot on the roadside is hard even for sober people. A defense review often focuses on whether:
•the surface was level and safe,
•the officer gave clear instructions and demonstrations,
•the person had footwear or mobility limitations,
•the test was cut short or restarted (and how that was documented).
Why Field Sobriety Tests Can Be Unreliable
In real DUI litigation, SFSTs are frequently attacked because they are human observations—not a machine reading—and small variables can change outcomes.
Common reliability problems:
•Instruction problems: Too fast, unclear, inconsistent, or not demonstrated.
•Environment problems: Uneven shoulder, wind, rain, glare, poor lighting.
•Footwear/clothing: Dress shoes, heels, restrictive clothing.
•Normal human factors: Stress response, fatigue, embarrassment, fear of arrest.
•Health factors: Back/knee injuries, vertigo, diabetes/neurological conditions, and more.
Bottom line: Even perfect SFST administration does not equal automatic guilt. The question is whether the government can prove impairment beyond a reasonable doubt, and SFST weaknesses can create reasonable doubt.
Field Sobriety Tests vs Breath/Blood Tests
A lot of people mix these up, so your page should be crystal clear:
Chemical tests are treated differently under California law
California DMV materials state that when you drive in California, you consent to a breath, blood, or urine test if an officer suspects DUI, and refusal can trigger DMV suspension/revocation and other consequences.
California Vehicle Code § 23612 (implied consent) likewise states that a driver is deemed to have consented to chemical testing if lawfully arrested for DUI-related offenses.
How a DUI Lawyer Challenges Field Sobriety Tests
A strong DUI defense doesn’t just say “the tests are unfair.” It shows why this specific SFST evidence is unreliable or overstated.
1) Attack the foundation: training + standardization
Because SFSTs are “standardized,” defense lawyers often focus on whether the officer followed standard procedures and whether the report shows proper administration. Training materials emphasize the existence of specific “clues” and standardized scoring concepts.
2) Use video against the report
Bodycam and dashcam footage can undermine:
•“swaying” claims
•“slurred speech” claims
•whether the line was real/visible
•whether instructions were rushed
•whether traffic noise or lighting interfered
3) Highlight alternate explanations
A good defense narrative connects poor performance to non-alcohol factors:
•old injury / mobility limitation
•unsafe surface conditions
•footwear
•fatigue / long day
•nervousness and confusion
4) Limit the “scientific” aura of HGN
HGN often gets treated as highly persuasive. But it’s still an observation test that depends on proper administration and accurate interpretation; resources describing HGN scoring show it’s based on counting observed “clues.”
5) Reframe the real legal question
Even if someone looks “off” on roadside exercises, the case still must prove impairment under the applicable DUI charge theory (your DUI defense page should link out and explain those legal elements).
What You Should Do During a DUI Stop
General practical tips (not legal advice):
•Be polite and calm.
•Don’t argue roadside—save facts for your attorney.
•If safe, mentally note conditions: lighting, surface, footwear, weather, traffic.
•Ask your lawyer ASAP so evidence requests (video, logs, reports) can start early.
Field Sobriety Test FAQs
Are SFSTs the same as a breath or blood test?
No. DMV guidance and Vehicle Code § 23612 address chemical testing (breath/blood/urine), which is treated differently—especially after a lawful DUI arrest.
What are the three “standardized” DUI field tests?
NHTSA refresher materials identify the SFST battery as HGN, Walk-and-Turn, and One-Leg Stand.
What “clues” do officers look for on Walk-and-Turn and One-Leg Stand?
Training materials emphasize distinct clues for each test, and SFST scoring sheets commonly list the classic WAT and OLS clues officers check off.
Why do sober people fail field sobriety tests?
Because SFSTs are sensitive to non-alcohol factors like balance, anxiety, injuries, uneven pavement, and unclear instructions.