Vehicle Code 40300.5 is a small statute with outsized importance in DUI cases. It is the special rule that lets an officer arrest a suspected drunk driver without a warrant even when the officer did not see the driving. I am Joel Brand, and understanding its limits is often the key to challenging a DUI arrest.
The text of the law
Vehicle Code 40300.5. In addition to the authority to make an arrest without a warrant pursuant to paragraph (1) of subdivision (a) of Section 836 of the Penal Code, a peace officer may, without a warrant, arrest a person when the officer has reasonable cause to believe that the person had been driving while under the influence of an alcoholic beverage or any drug, or under the combined influence of an alcoholic beverage and any drug when any of the following exists: (a) The person is involved in a traffic crash. (b) The person is observed in or about a vehicle that is obstructing a roadway. (c) The person will not be apprehended unless immediately arrested. (d) The person may cause injury to themselves or damage property unless immediately arrested. (e) The person may destroy or conceal evidence of the crime unless immediately arrested.
Why this statute exists
Normally, an officer cannot arrest someone for a misdemeanor without a warrant unless the offense happened in the officer's presence. A standard first-offense DUI is a misdemeanor, so this "in the presence" rule would be a problem in the many cases where police arrive after the driving is over, at a crash, a roadside, or a parked car. Section 40300.5 carves out an exception: in the specific situations listed, an officer with reasonable cause can make a warrantless DUI arrest even though no one saw the person drive.
The five situations, and their limits
The exception is not open-ended. It applies only when one of the five listed conditions exists: a traffic crash, a vehicle obstructing a roadway, a risk the person will not be caught unless arrested now, a risk of injury or property damage, or a risk of destroyed or concealed evidence. If none of those conditions is actually present, the warrantless misdemeanor DUI arrest may be unlawful. That is the gap I look for, because officers sometimes invoke 40300.5 loosely, stretching one of these categories to fit a situation that does not really qualify.
Why an unlawful arrest matters so much
When a DUI arrest is unlawful, the evidence that flowed from it, the chemical test, the post-arrest statements, and more, can be suppressed under a motion to suppress. Because so much of the prosecution's case depends on the breath or blood result obtained after arrest, suppressing it frequently guts the case. So whether the arrest fit within 40300.5 is not a technicality; it can decide the whole matter, which is why I treat it as one of the first questions in any case where the officer arrived after the driving was over.
How it connects to the no-driving defense
This statute most often comes into play in exactly the cases where the no-driving defense and the sleeping-in-the-car scenarios arise: the officer never saw the car move. In those cases I attack on two fronts at once. First, whether the arrest itself was authorized under 40300.5. Second, whether the state can even prove you were driving, which is a separate element it must establish beyond a reasonable doubt.
How I challenge a 40300.5 arrest
I examine the police report and the video to see which of the five conditions the officer relied on and whether the facts actually support it. Was there really a crash, or just a car legally parked? Was the vehicle truly obstructing a roadway? Was there any genuine risk that justified an immediate arrest? Where the claimed justification does not hold up, I move to suppress the evidence. It also ties into the broader review of the mistakes police make at a DUI stop. See my top DUI defenses.
The DMV side
The lawfulness of the arrest is also a required element at the DMV hearing. If the arrest did not satisfy 40300.5, that can defeat the administrative license suspension as well as support suppression in the criminal case, which is one more reason to demand the hearing within the 10-day window and to raise the issue on both tracks at once.
Reasonable cause is still required
Section 40300.5 does not lower the standard for the arrest itself; it only removes the in-the-presence requirement in the listed situations. The officer must still have reasonable cause to believe the person had been driving under the influence. That means the usual building blocks, the objective signs, the field sobriety tests, any admissions, still have to add up to a fair probability of a DUI. If the reasonable cause is thin, the arrest can be challenged on that ground even when one of the five conditions technically exists. I scrutinize both halves: whether a qualifying condition was present and whether genuine reasonable cause supported the arrest.
What the statute does not authorize
It is just as important to understand the limits. Section 40300.5 does not authorize an unlawful entry into a home, it does not excuse a stop or detention that lacked justification in the first place, and it does not relieve the prosecution of proving you actually drove. An officer cannot use it to paper over a stop that should never have happened. When the underlying detention was improper, the fact that 40300.5 might have allowed the later arrest does not save the evidence, because the problem started earlier in the chain. Tracing that chain from the first contact to the arrest is exactly how these cases are won.
Arrested without an officer seeing you drive? Let's talk.
Whether the warrantless arrest was lawful is often the central question, and it is exactly what I review. Use the free case analysis on this page, or call me directly at (888) 271-6644. I answer my own phone, 24/7.