To be arrested without having your Constitutional rights violated, the arresting officer must have what is known as “probable cause” to initiate a traffic stop on suspicion that the driver is under the influence of drugs or alcohol. Probable cause requires a reasonable, articulable suspicion, that the driver is in fact under the influence, or that some other crime is being committed. Typically, this occurs in the context of a simple traffic stop; the officer, utilizing radar, observes an individual speeding and then pulls them over for speeding. To bring it all together, this is Constitutional because the officer has a reasonable articulable suspicion (“I observed the readout on my radar gun”) that a crime is being committed (“speeding is against the law”), and thus was allowed to make the stop. The officer may subsequently develop suspicions that the driver is also under the influence, and will conduct himself accordingly. Sometimes however, he driver is operating the vehicle in a way that leads the officer to have a reasonable articulable suspicion that the driver is under the influence. For example, if the officer observes the driver swerving, or being unable to remain in one, that would satisfy the probable cause requirement for the stop.

Pursuant to the California Supreme Court, the Los Angeles Police Department has the authority to set up DUI check points, while it was a controversial decision, with a spirited dissent, the general concept I that a DUI checkpoint is an administrative activity1 . A brief discussion of the history of the law surrounding DUI checkpoints will take place below, but first, the Supreme Court imposed the following restrictions on DUI checkpoints:

  • There must be a police officer present at the DUI checkpoint, whose sole duty is to implement procedures, and make operational decisions, with the end-goal of consistency in the application and implementation of the law.
  • The officers cannot target specific cars for the stops; it must be based on a neutral, predetermined plan in order to avoid any bias. A common example of this is officers are told by the supervising officer that they are to stop every third car.
  • The location of the checkpoint must be reasonable, that is a DUI checkpoint in a random residential neighborhood where there has never been a DUI arrest would be objectively unreasonable. Whereas, a DUI checkpoint on a major thoroughfare where a large number of DUIs have occurred in the past would be sufficiently reasonable to pass constitutional muster.

1 Ingersoll v. Palmer (1987) 43 Cal.3d 1321 [241 Cal.Rptr. 42, 743 P.2d 1299];

  • The DUI checkpoint must contain sufficient safety measures, and those safety measures must be established at all times. For example, the road block must be visible to all oncoming drivers, and the checkpoint must be set up in such a fashion as maximize traffic flow through the area.
  • The time the DUI checkpoint begins must be determined, and occur, at a reasonable time. For example, a DUI checkpoint in the middle of the week, at 5pm during rush-hour on a major street is unlikely to be appropriate.
  • Every DUI checkpoint must have clear signs, indicating the nature of the stop. Drivers approaching the checkpoint must be able to identify that they will be going through a DUI checkpoint, and may need to stop soon. There are a number of ways to satisfy this requirement including flashing lights, signs, a marked patrol car, officers in full uniform, or flashing lights.
  • If a driver is stopped based on the neutral and unbiased policy put into effect by the supervising officer, the stop should take a minimal amount of time. The length of the stop should be long enough for the officer making the stop to look for signs of intoxication. This includes watery eyes, or bloodshot eyes, the smell of alcohol, or something else that would indicate to an ordinary person that the individual is currently under the influence of a drug or alcohol. If the driver does not present these symptoms, the officer should allow that driver to continue on. An officer is only allowed to investigate further if probable cause to believe someone is under the influence is present. Remember, probable cause requires a reasonable articulable suspicion.
  • Information about DUI checkpoints, including the time and location, must be made available to the public at least one week before it is scheduled to occur. Generally, these notices can be found in the local newspaper, some news stations, and the website for the police department.


There is no law in California at this time that prohibits the act of purposefully avoiding a DUI checkpoint. As long as you do not commit any traffic infractions in your efforts to avoid the checkpoint, you have not broken any law by avoiding a DUI checkpoint. As a result of the California Supreme Court’s requirements as it relates to DUI checkpoints, the police department must provide sufficient signage and warning to drivers that they are about to enter a DUI checkpoint zone. As such, you are free to turn off whatever street the checkpoint is on and avoid it altogether. There have not been any major cases regarding whether an officer will develop probable cause to make a stop if they see someone avoiding the checkpoint, but it would certainly be a questionable case that would be worthy of vigorous defense on Constitutional grounds. Notwithstanding that, most departments have a policy, which does not permit an officer to stop someone they observe avoiding the checkpoint.

In the event that you go through a DUI checkpoint, and you are not in possession of your California driver’s license, the officer may charge you with failure to possess your license pursuant to California Vehicle Code §12951. This charge is easily dismissed if your attorney and you can show that you had a valid license at the time of the stop, it just was not on your person at the time. If you did not have a valid license for any reason at the time, you are in violation of California vehicle Code §12500. If you are driving on a suspended license you are in violation of California Vehicle Code §14601. If that is the only offense you are charged with, and the vehicle is registered in your name, your car will not be impounded as a result of this charge.

Alternatively, if during the stop the officer develops probable cause that you are driving under the influence in violation of California Vehicle Code §23152, they may investigate that suspicion further, without violating your constitutional rights. Things that may trigger reasonable suspicion on the part of the officer include slurring, fumbling with your keys, having trouble getting your license, and smelling alcohol.


A brief history of DUI checkpoints is in order. First, it should be noted that in the recent years, DUI checkpoints have come under fire for a number of reasons. We will get to that in a moment. The first case truly relevant to the DUI checkpoint on the national level was a case known as Delaware v, Prouse 2 . This case focused on random stops as opposed to roadblocks, but the Court found that the random stops violated an individual’s 4th Amendment right because the officer could not have a reasonable articulable suspicion that a crime had been committed3 . In 1986, the concept of DUI checkpoints received the attention of the California Supreme Court . In a controversial decision, the Ingersoll Court determined that DUI checkpoints constituted an “administrative” procedure as opposed to a criminal procedure5 . The Court then stated that DUI checkpoints would not violate a person’s Constitutional rights, so as long as it complied with the restrictions mentioned above. This has been the law for the last three decades; failure to comply with any of the requirementshowever, can invalidate much of the evidence the officers would collect against you, and would likely result in the dismissal of a case against you.

2 Delaware v. Prouse, 440 U.S. 648, 99 S. Ct. 1391, 59 L. Ed. 2d 660 (1979)

3 The word “dragnet searches” is a common phrase in 4th amendment cases involving probable cause; it will always be a violation of the 4thAmendment if officers are searching an area in the hopes of catching someone committing a crime, the probable cause must be specific to the person.

4 Ingersoll v. Palmer, 43 Cal. 3d 1321, 241 Cal. Rptr. 42, 743 P.2d 1299 (1987)

5 This distinction has formed the basis of many attacks against this decision.

As noted, the Ingersoll decision is not without its critics. These criticisms have led to a few changes in DUI law; specifically: (1) officers can longer impound someone’s vehicle simply for not having a license with them, (2)


If you have been arrested as a result of a stop at a DUI checkpoint, contact an attorney from Los Angeles DUI Attorney Law Firm immediately, while the event is still fresh in your memory. A successful defense against a DUI that is premised on a DUI checkpoint stop will be very fact specific. As mentioned above, if the DUI checkpoint failed to comply with the laws set forth by the California Supreme Court, much the evidence must be excluded pursuant to the “exclusionary rule.” Naturally then, your defense will be very fact-specific; tell your attorney all the information you recall including: the time of day, where the stop occurred, how many cars were ahead of you, how many of those cars were stopped, how long the officer spoke to you before investigating further, as much as you can remember. The more facts that you arm your attorney with, the better the defense they can fashion for you. Contact our Los Angeles DUI AttorneyLaw Firm at 424-285-5400 for a FREE consultation.