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Fourth Amendment in DUI Cases

Posted by Robert Berglund | Sep 03, 2026

The Fourth Amendment of the Constitution provides that all people in the United States should be free from unreasonable searches and seizures.  While technically the Fourth Amendment only applies to action by the federal government, this right applies to the states through the Due Process Clause of the Fourteenth Amendment.  This means that searches and seizures of persons, including arrests, by California law enforcement agencies are within the scope of the Fourth Amendment and must be reasonable.  A seizure occurs when a reasonable person would believe that he or she is not free to leave or end the encounter with the law enforcement officer.  If police have reasonable suspicion of criminal activity or involvement in a completed crime, supported by articulable facts (not guessing or a hunch), they may detain a person for investigative purposes.  There does not need to be an arrest for there to be a seizure.  

These constitutional laws control how officers may conduct investigations and arrests in DUI cases.  Generally police may not stop a vehicle unless they have reasonable suspicion that a law has been violated.  When it comes to DUI cases, this is frequently a traffic violation.  Police observe a driver speeding, driving too slowly, weaving outside the lane, rolling through a red light, etc.  Officers then initiate a traffic stop.  This action constitutes a seizure.  Police are allowed to detain the driver long enough to get the appropriate information (license, registration, proof of insurance) and then issue a traffic violation citation.  Absent any active warrants, or other aggravating circumstances, police may not arrest a driver for a traffic infraction.  However, if during the encounter police observe objective symptoms of intoxication (bloodshot watery eyes, slurred speech, odor of alcohol, etc.) they now have reasonable suspicion to detain the driver for a DUI investigation.  A seizure of the driver has now occurred. If the investigation results in probable cause for the officers to believe the driver is DUI then he or she will be arrested.

On the other hand, if police do not have reasonable suspicion to initiate a traffic stop upon a driver then an illegal seizure has occurred.  This action violates the Fourth Amendment's prohibition that all people should be free from unreasonable searches and seizures.  For example, a police officer that stops a vehicle simply because it is exiting the parking lot of bar at 2:00 am, and has not violated any traffic laws, is violating that person's Fourth Amendment rights.  In this scenario, the officer likely stopped the car because he guessed that the driver leaving the bar at 2:00 am had been drinking and was DUI.  Even if the officer turned out to be correct and his illegal stop leads to a DUI arrest, it does not justify the illegal seizure in the first place.  The DUI case against this driver would be dismissed due to the Fourth Amendment violation.  

Similarly, if the driver does not display objective symptoms of intoxication during the initial traffic stop, the officer cannot seize the person further to conduct a DUI investigation.  This continued detention of the drive would be illegal.  A good DUI Lawyer will get this case dismissed due to the violation of constitutional rights.  

If a driver is lawfully detained because they displayed objective symptoms of intoxication, the investigation must still reach the conclusion conclusion that the driver is DUI.  If the investigation reveals something else other than DUI, for example the driver is suffering from an allergy attack or some other medical condition, the breathalyzer does not detect any alcohol and there is no evidence of drug use, then there is not probable cause to arrest the driver for DUI.  Maybe the driver should not continue driving due to a certain condition.  That does not mean he or she is DUI and should be arrested.  If there is not probable cause to arrest the driver for DUI, yet officers do so anyways, then a Fourth Amendment violation has occurred.  

A good DUI Lawyer will carefully examine all discovery available, including the investigation reports, dashcam video, body camera video, and audio used by law enforcement officers during the DUI investigation.  If it appears that there was not reasonable suspicion for the stop, or reasonable suspicion to detain for a DUI investigation, or probably cause to arrest following the DUI investigation, a motion to suppress evidence can be filed which, if granted, will result in a dismissal of the DUI case.  

If you have been arrested on suspicion of DUI, CONTACT our office today for a free and confidential consultation.  DUI Lawyer Robert D. Berglund will personally call you to discuss what happened in your case and provide you with an honest evaluation of how to best proceed.  Do not delay as you only have 10 days from the DUI violation date to contact the DMV to request a hearing.  

About the Author

Robert Berglund

Attorney Robert D. Berglund is dedicated to handling any and all traffic violations, including traffic infraction tickets, as well as misdemeanor criminal traffic violations, such as driving under the influence (DUI), driving on a suspended license, and reckless driving.

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