It depends which test. There are two, and they have opposite rules.
The pre-arrest roadside breath test is usually optional. The post-arrest chemical test is mandatory under implied consent — and refusing it costs your license for a year.
The Two Breath Tests
The pre-arrest test is the PAS (preliminary alcohol screening) — a handheld breath test at the roadside, part of the investigation. For a driver 21 or older who is not on DUI probation, the PAS is generally optional, like a field sobriety test. The post-arrest test is the evidential chemical test (breath or blood) after a lawful arrest — and that one is not optional.
Implied Consent (VC 23612)
Under Vehicle Code 23612, anyone who drives has given implied consent to a chemical test of blood or breath if lawfully arrested for a DUI. Refusing the post-arrest test triggers a separate administrative license suspension — one year for a first refusal (two years for a second within ten, three for a third) — and can add a fine and mandatory jail if you are convicted. The officer is required to advise you of these consequences.
What This Means for You
The practical takeaway: for most drivers, declining the roadside PAS and field sobriety tests is your right and takes away evidence. But once lawfully arrested, refusing the chemical test usually hurts — you lose your license for a year and hand the prosecution a refusal enhancement. If you refused, all is not lost: the lawfulness of the arrest, and whether the officer properly advised you, can be challenged at the DMV hearing and in court.
Frequently Asked Questions
Can you refuse a breathalyzer in California?
It depends which test. The pre-arrest roadside PAS breath test is generally optional for a driver 21 or older who is not on DUI probation. The post-arrest evidential chemical test is mandatory under implied consent (VC 23612), and refusing it results in a one-year license suspension plus a possible enhancement.
What happens if you refuse a chemical test after a DUI arrest?
Under VC 23612, refusing the post-arrest chemical test triggers an administrative license suspension — one year for a first refusal — separate from the criminal case, and it can add a fine and mandatory jail if you are convicted. The officer must advise you of these consequences.
What is the difference between the PAS and the chemical test?
The PAS (preliminary alcohol screening) is a pre-arrest roadside breath test that is generally optional for drivers 21+ not on DUI probation. The evidential chemical test is given after a lawful arrest and is mandatory under implied consent — refusing it costs your license.
GuidesComplete Guide to California Misdemeanors · Glossary · Penalties Reference.
Free 30-Minute Consultation
Refused a test and lost your license? The stop and the advisement may still be challengeable. Tell me what happened.
Schedule Free ConsultationAbout the Author
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