“Probable Cause” in California – 4 Examples Where It Applies

In California, police have probable cause when there is sufficient evidence to convince a reasonable person that a crime has been committed. Probable cause is a higher standard than “reasonable suspicion” but a lower standard than “beyond a reasonable doubt.”

As I explain below, the term probable cause is used in four primary situations in California criminal cases:

1. Detainments and Traffic Stops
2. Arrests
3. Search Warrants, and
4. Preliminary Hearings.

1. Detainments and Traffic Stops

Many people believe that California police need probable cause in order to detain you or conduct a traffic stop. However, the police need only a reasonable suspicion, which means that a reasonable person could infer from the facts you may have committed a crime or traffic infraction.

In practice, detainments and traffic stops are opportunities for police to find evidence of a crime so they can get probable cause.

Example: An officer sees a car on the highway swerving. The swerving gives the officer reasonable suspicion that the driver might be under the influence of drugs or alcohol in violation of the California Vehicle Code, though the swerving could be due to something non-criminal like a muscle spasm or fatigue. Therefore, the officer pulls the driver over to investigate further.

If your detainment or traffic stop does not yield more evidence of a crime, you should be allowed to get on your way. If the officer finds probable cause that you broke the law, then you can be arrested (as discussed in the next section).

Note that police can frisk you during a detainment only if they have a justifiable belief you are armed and dangerous. Stop-and-frisks are also called “Terry Stops.”¹

2. Arrests

For a California judge to issue a warrant for your arrest, the police’s warrant application and affidavit must show there is probable cause that you committed a crime. For police to arrest you without a warrant, the officer needs probable cause to believe that you:

• committed any crime in the officer’s presence or
• committed a felony, whether or not in the officer’s presence.

Typical supporting evidence of probable cause includes eyewitness accounts, surveillance video, and recorded communications.

Probable cause requires more proof than a reasonable suspicion, but there can still be a reasonable doubt. Many people who are arrested for a crime never get convicted due to there being a reasonable doubt.²

I have had many cases where clients were arrested without probable cause, called a “false arrest.” If the judge agrees that you were apprehended based only on a reasonable suspicion, your case could be dropped.

California police need only reasonable suspicion to make a traffic stop.

3. Search Warrants

The Fourth Amendment to the U.S Constitution prohibits “unreasonable searches and seizures.” Before a California judge can issue a search warrant, they must have probable cause that:

1. a crime was committed, and
2. the locations specified in the warrant application have evidence of a crime (such as drugs, weapons, or other contraband).

Judges make a probable cause determination by looking at the claims presented in an officer’s warrant application and affidavit. In many cases, the evidence that police find through a search warrant gives police probable cause to then arrest the suspects.

Note that police can conduct warrantless searches of pedestrians and cars as long as they have probable cause. Since pedestrians and motorists have a decreased expectation of privacy, police do not have to get a warrant first.³

In my experience, police often lack the justification to make a warrantless search, or if do get a search warrant, they go beyond the bounds of the judge’s instructions. When this happens, I ask the judge to suppress any evidence that was obtained through the unlawful search: If the judge agrees, the state’s case may fall apart.

Probable cause is necessary to make an arrest in California.

4. Preliminary Hearings

Soon after you get charged with a felony in California, you are entitled to a preliminary hearing (“prelim”). This is where the district attorney presents evidence to the judge to show there is probable cause that you committed the charged offenses.

Prelims serve as a “check” where judges make sure sufficient evidence exists to continue prosecuting you. If there is not probable cause, your charge should get dismissed. If there is probable cause, the judge will then “hold you to answer” for the charge by “binding” your case over for trial.

Remember, prelims are not trials, where prosecutors have to prove your guilt beyond a reasonable doubt to convict you. Beyond a reasonable doubt is a far higher standard than probable cause, and many people who lose their prelims do not ultimately get convicted at trial.

The only time you do not get a prelim is if a grand jury indicted you (which happens in just a few state cases). This is because an indictment means the grand jury already found probable cause, so doing a prelim would be unnecessary.

Prosecutors must show probable cause in order to win a preliminary hearing.

Additional Reading

For more in-depth information, refer to these scholarly articles:

• Probable Cause, Probability, and Hindsight – Journal of Empirical Legal Studies
• Putting Probability Back into Probable Cause – Texas Law Review
• Probabilities in Probable Cause and Beyond: Statistical Versus Concrete Harms – Law and Contemporary Problems
• Probable Cause Pluralism – Yale Law Journal
• Probable Cause Revisited – Stanford Law Review