The Fourth Amendment to the Constitution protects American citizens from "unreasonable searches and seizures," along with warrants issued "without probable cause."

Probable cause means reasonable suspicion you committed a crime or that there is evidence at a location.

This raises the question about what constitutes "probable cause" and when it applies—and probing this ambiguity is often a key strategy among California criminal defense attorneys.

If an attorney can show that the government did not have probable cause when arresting you or searching and seizing your property, any case against you could be significantly weakened.

In short, neither law enforcement nor the state can violate your constitutional rights when pursuing a case against you, regardless of your guilt or innocence.

So, what exactly is “probable cause” in a criminal case? Simply put, it is evidence that would compel a reasonable person to believe that a crime occurred or there is evidence of illegal activity in a specific location to be searched.

In California, probable cause can apply to different situations. For example, consider the following scenarios:

• Did the police have probable cause to arrest you for a crime?
• Did they have probable cause to detain you after a traffic stop?
• Did the police present sufficient probable cause to the judge for a search warrant?
• Did the prosecutor present enough probable cause to have you held to answer for criminal charges after a preliminary hearing?

An area where probable cause is often misunderstood is related to traffic stops. Police only need “reasonable suspicion,” a lower standard than probable cause.

In other words, to pull you over on a traffic stop, police only need a reasonable suspicion that you committed a traffic infraction that violated any section of the California Vehicle Code.  Notably, the reasonable suspicion standard applies in DUI cases.

What is the Definition of Probable Cause?

Probable cause refers to having a reasonable belief, backed by a reasonable (but not necessarily irrefutable) amount of evidence, that someone has likely committed a crime. Probable cause sets a requirement for actions, such as the following:

• Traffic stops,
• Arrests,
• Search warrants, and
• Investigations.

By demanding a reasonable basis for suspicion, probable cause upholds the rule of law and safeguards individual rights in our society.

It should be noted that the evidence against you does not have to be conclusive for probable cause to apply—because you have not yet been convicted of a crime.

Probable cause is defined as “a requirement found in the Fourth Amendment that must usually be met before police make an arrest, conduct a search, or receive a warrant. Courts usually find probable cause when there is a reasonable basis for believing that a crime may have been committed (for an arrest) or when evidence of the crime is present in the place to be searched (for a search). Under exigent circumstances, probable cause can also justify a warrantless search or seizure. Persons arrested without a warrant must be brought before a competent authority shortly after the arrest for a prompt judicial determination of probable cause.”

Probable cause only relies on having enough evidence to suspect you of a crime, not necessarily to convict you. Once the probable cause standard is met, the job of your defense attorney is to show that whatever evidence exists is not enough to convict you beyond a reasonable doubt. Under California law, the probable cause standard applies in each of the situations discussed below.

What About Traffic Stops?

Traffic stops are among the most common scenarios where probable cause comes into play. Officers may stop drivers if they reasonably suspect that a traffic violation or crime has occurred.

This suspicion could be based on observed behavior like erratic driving. If, during the stop, the officer detects further indications of criminal behavior, this may constitute probable cause to arrest you without the need for a warrant. Consider the following examples below:

• Example 1: An officer using a radar gun clocks Jesse driving at 20 mph over the speed limit. While not conclusive evidence, the radar gun provides probable cause that Jesse was speeding, and the officer may pull him over and write a ticket.
• Example 2: An officer notices Terry drifting lanes on the highway without signaling, generating a reasonable suspicion of DUI and giving the officer probable cause to pull Terry over.

What Standard Applies to Arrests and Arrest Warrants?

Arrests without a warrant necessitate probable cause. A police officer can only arrest you with no arrest warrant if:

• They have a reasonable belief based on the observation that you committed a crime;
• That you committed a felony, whether or not in their presence.

Likewise, a judge with probable cause can only issue an arrest warrant based on evidence that a crime likely occurred.

Example: Referring to the second example above, if after stopping Terry for drifting lanes, the officer notes the smell of alcohol and Terry's slurred speech, the officer may arrest Terry without a warrant on probable cause that DUI has occurred.

What About Search Warrants?

Probable cause is also a prerequisite for obtaining search warrants. Law enforcement must present sufficient evidence to a judge to persuade them of the following:

• That a crime has likely occurred, and
• That evidence of the crime will likely be found at a specific location.

Simply put, a judge typically determines probable cause by examining the facts presented in an officer's warrant application (affidavit).

For instance, if police suspect stolen items are housed in a particular residence, they must provide supporting evidence to justify a search warrant.

Example: Investigators have home security video footage that appears to show Darryl burglarizing a home. Police suspect the stolen property from the burglary is stored in Darryl's apartment. This provides probable cause for the judge to issue a search warrant.

What Standard Applies to Preliminary Hearings?

Finally, in California, a judge can only send a felony case to trial with probable cause as determined by a preliminary hearing. This hearing decides whether there is enough evidence to “hold you to answer” for the charges and proceed to a trial.

In other words, if you are arrested and charged with a felony, the judge will hold a preliminary hearing to decide whether the current evidence provides a reasonable belief that you committed the crime.

After hearing evidence presented by the prosecutor, your defense attorney has the opportunity to challenge the sufficiency of evidence supporting the charge(s).

If the judge concludes that there is not enough evidence to justify a trial—or if it is determined that probable cause was not met at other stages of the case, for example, if police conducted an unlawful search or had no probable cause for an arrest—the judge will dismiss the charges for lack of probable cause.

The standard used in these hearings is a probable cause standard, which is a lesser standard than the “beyond a reasonable doubt” standard used in criminal trials. Contact our law firm for a case review. Eisner Gorin LLP has offices in Los Angeles, CA.

Related Content:

• What is a Ramey Warrant?
• What Is Qualified Immunity?
• How MVARS Can Help or Hurt Your DUI or Criminal Case
• Merchant's Privilege and the Right to Detain
• When Can Police Search Your Cell Phone?
• What is Proof Beyond a Reasonable Doubt?
• Terry v. Ohio 392 U.S. 1, 20 L. Ed. 2d 889 (1968)
• People v. Chalak 48 Cal. App 5th Supp. 14 (2020)
• Probable Cause Definition
• Probable Cause Annotations
• California Penal Code 817 PC
• California Penal Code 1525 PC