Field sobriety tests like the walk-and-turn, one-leg stand, and eye-tracking exercises, are designed as observational tools to help officers establish probable cause. They are not scientific pass-or-fail exams, and performance can be affected by fatigue, stress, injury, footwear, or environmental conditions. Despite this, they are frequently used as a primary basis for arrest.
Understanding probable cause is key to understanding how DUI arrests happen. In simple terms, probable cause means an officer has enough observable information to reasonably believe a crime has been committed. In a DUI context, that can include driving behavior (swerving, speeding), physical signs (bloodshot eyes, odor of alcohol), specific statements made by the driver, or performance on field sobriety tests. It does not require proof beyond a reasonable doubt, just enough to justify an arrest and further testing.
In California, including throughout San Diego County, drivers have the right to decline field sobriety tests. Refusing may not stop an arrest, but it does limit the amount of subjective evidence being created during the stop.
Drivers should also understand that they are not required to answer investigatory questions. Officers may encourage a person to provide information about where they are coming from, whether they have been drinking, or how much they have consumed. It should be known that people have the right to politely decline to answer those questions. Many legal professionals advise keeping responses minimal and respectful, focusing only on providing required identification and documentation. Frequent advice is to state: "I respectfully wish to remain silent and do not answer investigatory questions."
The same voluntary framework often applies to the handheld roadside breathalyzer, known as a Preliminary Alcohol Screening (PAS) test. For drivers over 21 who are not on DUI probation, this test is typically optional prior to arrest. One practical way to clarify your obligations is to ask, “Am I under arrest?” If the answer is no, the PAS test is generally still in the voluntary phase.
After a lawful DUI arrest in California, drivers are generally given the choice between a breath or blood test under the state’s implied consent law, and many defense attorneys note that opting for a blood test can introduce additional procedural considerations. Unlike a breath test, which is administered immediately at the station, a blood draw must be performed by qualified medical personnel, often requiring transport and creating a time gap between driving and testing. Additionally, blood samples are subject to strict handling, storage, and documentation requirements, commonly referred to as “chain of custody.” Any irregularities in how the sample is collected, labeled, stored, or transferred can become points of scrutiny in court. While both testing methods are legally valid, the additional steps involved in blood testing can create more areas for examination during a legal defense.
The renewed attention on DUI procedures also comes as sobriety checkpoints remain a regular fixture across San Diego. These checkpoints, often announced in advance by local law enforcement agencies, involve stopping vehicles at predetermined locations to screen for impaired drivers. Typically set up on weekends or near large events, they allow officers to briefly question drivers and look for signs of intoxication.
While checkpoints are legal in California, they must follow strict guidelines, including advance notice and neutral selection criteria for stopping vehicles. Drivers are required to comply with the initial stop, such as providing a license, but retain the same rights regarding field sobriety tests as they would during a standard traffic stop.
For San Diego drivers, the distinction between voluntary and mandatory compliance is not just technical, it can significantly impact the course of a DUI investigation. Understanding probable cause, knowing when you can decline participation, and recognizing when your legal obligations begin are essential components of navigating a DUI stop.
As more bodycam footage enters public view, the takeaway is increasingly clear: knowing your rights is not about resisting law enforcement, it is about understanding the legal framework that governs these encounters before you find yourself in one.
Know Your Rights Cheat Sheet (California DUI Stops):
You must comply with a lawful stop
Provide your driver’s license, registration, and proof of insurance when requested.
You are not required to answer questions
You may politely decline to discuss where you’ve been or whether you’ve consumed alcohol.
Field sobriety tests are generally voluntary
You can decline roadside physical tests without automatic penalties.
Roadside breathalyzer (PAS) is usually voluntary
If you are 21+ and not on DUI probation, you can typically decline the handheld breath test before arrest. Asking “Am I under arrest?” can help clarify your status.
After arrest, chemical testing is mandatory
Under California’s implied consent law, once arrested, you must submit to a chemical test.
You can generally choose breath or blood after arrest
In most DUI cases, drivers are given the option between a breath or blood test after arrest. If you prefer a blood test, for example, if you question the accuracy of breath testing, you can typically request it. However, refusal of both is treated as a violation and triggers automatic penalties.
