What Is Probable Cause in a Los Angeles DUI Case?

In a Los Angeles DUI case, probable cause refers to the legal standard that law enforcement must meet before they can pull a driver over or arrest them for driving under the influence. Probable cause means that the officer must have a reasonable belief, based on observable facts, that the driver has violated the law. In the context of DUI cases, this can be established through a variety of signs, including traffic violations like swerving, speeding, or failing to stop at a red light, as well as physical indicators like the smell of alcohol, slurred speech, or erratic driving behavior.

If an officer lacks probable cause for the traffic stop or arrest, any evidence obtained during the stop—such as results from a breathalyzer, field sobriety tests, or blood tests—can be challenged in court. In some cases, the entire case could be dismissed if it’s shown that there was no valid probable cause for the stop

How Does Probable Cause Affect a DUI Arrest in Los Angeles?

In Los Angeles, probable cause is the foundation of any lawful DUI arrest. Without it, any evidence gathered after the stop—including breathalyzer results, field sobriety tests, or blood tests—may be deemed inadmissible in court. This means that key evidence could be suppressed, significantly weakening the prosecution’s case and increasing the likelihood of a dismissal or reduction of charges.

Probable cause is essential to ensure that law enforcement has a legitimate reason to stop and arrest a driver. If it’s proven that the officer did not have sufficient grounds to make the stop, the entire arrest could be ruled illegal. In these cases, the charges may be dismissed altogether, making the role of probable cause critical in the legal process.

A DUI defense attorney will carefully review the circumstances of your arrest to determine if probable cause was present and challenge the evidence if it wasn’t.

What Constitutes Reasonable Suspicion vs. Probable Cause?

In DUI cases, understanding the difference between reasonable suspicion and probable cause is essential in determining whether a traffic stop and subsequent arrest were lawful.

Reasonable Suspicion: This is the lower standard that allows an officer to stop your vehicle if they suspect you may be engaged in illegal activity. For instance, behaviors such as swerving between lanes, speeding, or running a red light provide enough grounds for the officer to initiate a stop. However, at this stage, they do not yet have the authority to arrest you for DUI—just to investigate further.

Probable Cause: Once the vehicle is stopped, the officer needs probable cause to arrest you. This is a higher standard and requires specific facts to believe that the driver is intoxicated. Indicators like the smell of alcohol, slurred speech, bloodshot eyes, or failing a field sobriety test provide the officer with probable cause to make an arrest for DUI.

A DUI lawyer can challenge whether the officer had either reasonable suspicion or probable cause at any point during the stop or arrest. If it’s shown that these legal thresholds were not met, evidence obtained during the stop—such as breathalyzer or sobriety test results—may be suppressed, weakening the prosecution’s case.

Common Examples of Probable Cause in Los Angeles DUI Cases

In Los Angeles, officers need probable cause to stop and arrest a driver for DUI. This means they must observe specific behaviors or evidence that reasonably suggest the driver is under the influence. Here are some real-world examples that may provide an officer with probable cause in DUI cases:

Traffic Violations: Swerving between lanes, speeding, running red lights, or driving erratically can give officers reasonable suspicion to initiate a traffic stop. If additional signs of intoxication are present after the stop, this can lead to a DUI arrest.

Signs of Intoxication: During the stop, officers often rely on observable signs like the smell of alcohol, slurred speech, bloodshot or watery eyes, and difficulty responding to questions. These indicators, especially if combined, often provide the officer with probable cause to proceed with a DUI arrest.

Field Sobriety Tests: Officers typically ask drivers to perform field sobriety tests (FSTs) to assess physical coordination and cognitive abilities. Failing these tests—such as difficulty walking in a straight line or maintaining balance during the one-leg stand—can give the officer sufficient probable cause to make an arrest. Even refusing to take these tests can be used as justification for probable cause.

Breathalyzer Results: If a driver submits to a breathalyzer test and their Blood Alcohol Content (BAC) is 0.08% or higher, this gives the officer clear probable cause for a DUI arrest. However, breathalyzer results can sometimes be challenged based on the device’s accuracy or proper procedure.

What Happens If There Was No Probable Cause for Your DUI Arrest?

If a DUI arrest was made without probable cause, the legal implications can significantly impact the outcome of the case. Probable cause is the legal standard that ensures law enforcement had a reasonable basis for stopping and arresting the driver. Without it, any evidence gathered after the stop, such as breathalyzer results, field sobriety tests, or blood tests, could be suppressed in court. This means that the evidence cannot be used against the defendant, which can severely weaken the prosecution’s case.

For example, if an officer pulls someone over without witnessing any traffic violation or signs of impairment, such as swerving or speeding, the initial stop may be deemed illegal. If it can be proven that the officer lacked probable cause for the stop, any subsequent DUI charges based on the traffic stop could be challenged. In such scenarios, the evidence gathered after the stop—such as failed sobriety tests or a high Blood Alcohol Content (BAC)—would likely be excluded from the trial.

In some cases, if the evidence is essential to the prosecution’s argument, the entire case may be dismissed. This is common when the arrest hinges solely on evidence obtained after an unlawful stop. For instance, if the officer arrested someone solely based on a vague suspicion without observable signs like slurred speech or erratic driving, the court may suppress that evidence, potentially resulting in a dismissal.

An experienced defense attorney plays a critical role in this process by investigating the details of the arrest, reviewing police reports, dashcam footage, and cross-examining the arresting officer to determine whether probable cause was present. If it’s found that probable cause was lacking, the attorney can file a motion to suppress evidence, which can lead to a reduction or dismissal of charg

How a DUI Defense Attorney Can Challenge Probable Cause

Investigating the Traffic Stop

The first step is to thoroughly investigate the circumstances of the traffic stop. Your attorney will review dashcam footage, the police report, and any witness statements to determine whether the officer had valid probable cause to pull you over. For example, if you were stopped without any visible traffic violation or clear signs of impairment, such as swerving or speeding, the stop might have been unjustified. Your attorney can use this evidence to challenge the legitimacy of the stop.

Filing a Motion to Suppress Evidence

If it’s established that the officer lacked probable cause, your DUI defense attorney can file a motion to suppress any evidence obtained after the stop, such as breathalyzer results, field sobriety tests, or blood tests. Without this evidence, the prosecution’s case could weaken significantly. For example, if the stop was made purely on a hunch rather than on observed behavior, your attorney can argue that the evidence was obtained illegally, which may lead to a reduction or dismissal of charges.

Cross-Examining the Officer

During court hearings, your attorney will have the opportunity to cross-examine the arresting officer. This is an important step to challenge the officer’s version of events and their justification for the stop. If the officer’s testimony reveals inconsistencies or if they admit to lacking specific facts that would indicate probable cause, this could support your case for dismissing the charges. For instance, if the officer claims they smelled alcohol but dashcam footage shows no erratic driving, your attorney can highlight this to question the officer’s credibility.

Challenging probable cause is a powerful defense strategy that can substantially impact the outcome of your DUI case. With the right attorney on your side, you stand a better chance of having key evidence excluded or the charges dismissed altogether.

What If Probable Cause Is Established? Can You Still Fight the Charges?

Challenging the Accuracy of Breathalyzer or Blood Tests

Breathalyzer and blood tests are not foolproof. Our attorney will investigate whether the breathalyzer was properly calibrated or if the officer followed the correct procedures during testing. If the device wasn’t functioning correctly or the tests were mishandled, we can question the validity of the BAC results. Similarly, if there were errors in how a blood test was conducted or stored, we can argue that the results should be thrown out.

Questioning the Reliability of Field Sobriety Tests

Field sobriety tests can be inaccurate due to many factors, including weather conditions, uneven roads, or even medical issues. Our attorney will review whether these tests were administered correctly and whether other factors could have affected your performance. If the tests were flawed or unreliable, we will challenge their use as evidence.

Disputing the Officer’s Interpretation of Intoxication Signs

Signs like slurred speech, bloodshot eyes, or an odor of alcohol don’t always indicate intoxication. Fatigue, allergies, or other health issues can present similar symptoms. We will work to show that the officer’s conclusions about your condition were not as clear-cut as they claimed.

Even if probable cause was present, these strategies can lead to a reduction of charges or even dismissal, depending on the specifics of your case. Our goal is to explore every possible avenue to protect your rights and achieve the best outcome.

How Our Los Angeles DUI Defense Attorney Can Help You

Attorney Hashemi has over 20 years of experience defending clients in DUI cases and knows how to build a strong defense tailored to your situation. We will carefully review the details of your traffic stop and arrest to determine whether the police had reasonable suspicion or probable cause. If we find any flaws in the process, we will use them to challenge the validity of the stop and arrest.

Our team will also investigate every aspect of the evidence against you, including breathalyzer results, field sobriety tests, and officer reports, to ensure they were conducted correctly. If the police violated your rights, we will work to suppress the evidence, potentially leading to a dismissal of charges. Time is critical in DUI cases, and having skilled legal representation can significantly impact the outcome.

If you’re facing DUI charges, don’t delay—contact our office for a free consultation. We will review your case, explain your options, and build a strong defense to protect your future and driving privileges.