There’s a lot of confusion around this question, and for good reason. The answer depends entirely on when you’re being asked to take the test and what kind of test it is. If you’ve been pulled over on suspicion of driving under the influence, understanding the difference could shape the outcome of your entire case.
Two Different Tests, Two Different Rules
Most people don’t realize there are actually two separate breath tests involved in a typical DUI stop. Our friends at Seyb Law Group see this confusion regularly and it’s one of the first things they clarify with new clients.
The first is the Preliminary Alcohol Screening test, commonly called the PAS test. Officers administer this one roadside, using a handheld device, before placing you under arrest. It’s an investigative tool. Its purpose is to help the officer establish probable cause for an arrest, not to serve as the primary evidence of your blood alcohol concentration.
The second is the evidentiary chemical test. This one happens after you’ve been formally arrested and is typically conducted at the police station using a more sophisticated breath testing instrument, or through a blood draw. This is the test that carries serious legal weight and the one you can’t refuse without facing significant penalties.
Refusal Rules for Each Test
If you’re over 21 and not currently on DUI probation, you have the legal right to decline the PAS test. There’s no automatic penalty for saying no. Officers aren’t always forthcoming about this, and some may phrase the request in a way that makes it sound mandatory. It isn’t.
There are two exceptions:
- Drivers under 21. Under zero-tolerance laws, underage drivers are required to submit to the PAS test. Refusing can result in a license suspension.
- Drivers on DUI probation. If you’re on probation for a prior DUI conviction, the PAS test is mandatory. Refusal can trigger a probation violation and additional penalties.
For everyone else, the PAS test is voluntary. Declining it means the officer will need to rely on other observations, such as your driving pattern, your behavior during the stop, and the results of any field sobriety tests, to decide whether an arrest is warranted.
The post-arrest chemical test is different. Under Vehicle Code Section 23612, anyone who operates a motor vehicle is deemed to have given consent to chemical testing of their blood or breath if they are lawfully arrested for a DUI offense. You agreed to this when you received your driver’s license.
A Refusal Doesn’t Mean You’ll Avoid a Conviction
Some drivers refuse the post-arrest test thinking it will make the prosecution’s case harder to prove. Sometimes it does. But prosecutors can still pursue DUI charges without a BAC result. They’ll rely on the officer’s observations, dash cam footage, field sobriety test performance, and any other available evidence. They can also argue to a jury that the refusal itself shows a consciousness of guilt, that you refused because you knew you were over the legal limit.
A DUI lawyer can evaluate whether the refusal actually helps or hurts your defense, depending on the specific facts of your case.
What You Should Do During a DUI Stop
Stay calm. Be polite. Provide your license, registration, and insurance when asked. Beyond that, you aren’t required to answer questions about where you’ve been, how much you’ve had to drink, or where you’re headed. You have the right to remain silent, and exercising that right early can make a real difference later.
If you’ve already been arrested for DUI, whether you refused the chemical test or not, the most important thing you can do is speak with an experienced defense attorney as soon as possible. You only have 10 days from your arrest to request a DMV hearing to contest your license suspension, and that deadline won’t wait.