Field sobriety tests — the walk-and-turn, the one-leg stand, the eye test — are voluntary. You can usually decline them.
They are also unreliable, which is exactly why they get attacked in a DUI case.
They're Voluntary
There is no law requiring you to perform field sobriety tests. Unlike the post-arrest chemical test, declining an FST carries no automatic license penalty. Officers rarely mention that they are optional — but for most drivers, they are.
Why They're Unreliable
These tests are hard to ‘pass’ even sober. Fatigue, nerves, uneven pavement, poor lighting, bad weather, footwear, age, weight, injuries, and medical conditions all affect performance. They are subjective — scored by the same officer who decided to pull you over — which builds bias into the result.
How They Get Challenged
In a DUI case, the defense scrutinizes whether the tests were administered correctly, whether conditions were fair, and whether the officer’s conclusions actually follow from what the report and any video show. Where the case leans on FSTs rather than a solid chemical test, there is real room to fight — toward a dismissal or a wet reckless.
Frequently Asked Questions
Do you have to do field sobriety tests in California?
No — and this trips people up because officers frame it like it's mandatory. Field sobriety tests are voluntary, with no automatic license consequence for declining, unlike the breath or blood test after arrest. Most drivers can simply decline.
Are field sobriety tests accurate?
Not particularly — that's the point of attacking them. A sober person can fail these tests because of nerves, uneven ground, bad shoes, fatigue, age, weight, or a medical condition. And the officer who arrested you is also the one grading your performance, which is not exactly neutral.
Can field sobriety tests be challenged in a DUI case?
Yes, and often successfully. If the officer skipped steps in the test, conditions weren't fair, or the video doesn't back up the report's conclusions, that's an opening. A DUI resting mainly on FSTs — instead of a strong chemical test — is often the weakest kind for the prosecution to prove.
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Ahmed S. Hasan
San Francisco Criminal Defense Attorney · State Bar of California #364992
Ahmed S. Hasan is the founder of ASH Legal, a solo criminal defense practice based in San Francisco. The firm runs on flat-fee representation: one lawyer, one fee, from arraignment through resolution. No hourly billing. No surprise invoices.
Ahmed is a graduate of Emory University School of Law and a member in good standing of the State Bar of California (Bar #364992). His practice focuses on San Francisco misdemeanor defense — DUI, domestic violence, petty theft and shoplifting, drug possession, vandalism, trespassing, and assault and battery — with particular attention to diversion-track outcomes that end in dismissal under PC 1001.95, PC 1001.36 (Mental Health Diversion), PC 1001.80 (Military Diversion), and PC 1001.83 (Parental Caregiver Diversion).
Ahmed previously served as a post-bar clerk with the San Francisco Public Defender's Office, the city's largest indigent-defense practice. He is a member of the Asian Pacific American Bar Association of Silicon Valley.
He represents clients at the San Francisco Hall of Justice (850 Bryant Street) and the Civic Center Courthouse. The ASH Legal office is at 15 Boardman Place, Suite 301, San Francisco, CA 94103.
Free 30-minute consultations are available by phone or Zoom. (510) 545-6515 · ahmed@ashlegal.com