The concept of probable cause is a crucial legal standard in California’s criminal justice system. It ensures that law enforcement actions are not arbitrary or based merely on a hunch. It is rooted in the Fourth Amendment, which protects citizens from unreasonable searches and seizures. Probable cause is a reasonable belief, based on specific and articulable facts, that a crime has been or is being committed. It requires more than mere suspicion, but less than the proof needed for a conviction.

This standard distinguishes a valid police action from an unconstitutional one, serving as a check on government power and protecting individual liberties. Many major legal processes rely on probable cause, including arrests and search warrants. There are four typical scenarios where probable cause applies. These examples show how initial suspicion can develop into facts that support significant legal action.

Example 1: Probable Cause to Make an Arrest

One of the situations that most likely features probable cause is a DUI arrest. A police encounter may begin with a traffic stop based on the lesser reasonable suspicion standard. You may be pulled over because an officer notices you weaving in and out of your lane, driving with a broken taillight, or even when you do not stop at a red traffic light. The original violation gives the reasonable suspicion required to stop, but not enough to warrant an arrest.

Once the officer stops you, they are supposed to gather more evidence to formulate probable cause to arrest you concerning a DUI. This includes a chain of observations and activities to verify their suspicion that you are driving under the influence. The officer will seek several typical signs, and when combined, they will form the foundation of the case leading to arrest.

These indicators often include:

  • The smell of alcohol or marijuana that comes out of your car or yourself

  • Mumbled speech, fumbling with your license and registration, or watery red eyes

  • The fact that you are drinking or using drugs, even though you say that you had one

The accumulation of these facts, from the initial traffic violation to the physical signs of impairment and poor performance on FSTs, creates the probable cause needed to make a lawful DUI arrest. Inability to carry out these tests as required is a good indication of impairment.

The findings of a Preliminary Alcohol Screening (PAS) assessment, if you agree to take it. Although the roadside device is less accurate than a later blood or breath test, a positive result is additional evidence for a follow-up blood or breath test.

Example 2: Probable Cause to Obtain a Search Warrant

Obtaining a search warrant is another and more formal use of the probable cause standard, the most crucial distinction being that it is not the police but a neutral judge who makes the ultimate decision. This judicial check is essential to law enforcement authorities and will safeguard you against unjustified government invasion of your home or property.

The process starts when the law enforcement officers, having obtained evidence, assume that a search will help reveal evidence of a crime being committed at a certain point. They are not authorized to act on this belief alone. Instead, they are supposed to bring their case before a judge by submitting a formal document called a probable cause affidavit. It is an oath-taken document written by an officer, where the officer describes all the facts, observations, and evidence gathered. The affidavit should be detailed, presenting a convincing case that a crime has been committed and that a fair probability of the evidence of that crime will be found at the location where they desire to search.

The judge who receives the affidavit carries out a strict review. The judge must not simply approve the request without scrutiny, but act as an independent adjudicator to make the request constitutional. The judge uses the totality of the circumstances test, which considers all the information in the affidavit combined to determine whether it creates probable cause. They will question the informants' credibility, the information's specificity, and the evidence's timeliness. The judge may refuse the warrant if the affidavit does not present adequate and credible facts.

Courts use the totality of the circumstances test to determine whether police acted with probable cause or reasonable suspicion when taking action against you. This fact-specific, flexible approach will evaluate the law not on a single fact but on the overall situation. A judge will not use a strict checklist but will consider all the information accessible to the police officer at the moment, including their training and experience, and the surrounding circumstances. This will enable the courts not to engage in an overly technical interpretation and to apply a practical, common-sense interpretation of the facts, realizing that what might be inconsequential when taken with other circumstances may have much to tell.

It is a comprehensive review, which means that a probable cause can be found against you on several factors. For example, an anonymous tip is not a matter of weight by itself, but it receives a great deal of weight if an officer corroborates some information. Similarly, your attempt to flee, although not direct evidence of guilt, may be considered along with other factors when taken together with different pieces of evidence, like the smell of drugs or the presence of a weapon. When combined, these details may justify a legal search or arrest. The standard prevents police from relying on a single isolated fact.

The totality of the circumstances is the test that critically protects your constitutional rights. The rule ensures that law enforcement's power to detain, search, and arrest you is not exercised randomly by requiring a thorough evaluation of any available facts. This standard balances between police being given the power to investigate and prevent crime, and you not being unreasonably intruded upon by the government. Both law enforcement and citizens must understand this rule, which defines the boundary between lawful and unlawful police action.

The warrant must clearly specify the search location and the items to be seized. This is mandatory and thus does not allow a broad, exploratory search, which restricts the intrusion of the police. The final legal authorization is the judge's signature on the warrant. It establishes that a search is justified and legal based on the evidence provided in the affidavit. Thus, the lynchpin to this process is the probable cause affidavit and independent review by the judge, which means that your Fourth Amendment rights are met before police enter and search your private space.

Example 3: Probable Cause to Arrest For a Crime

Perhaps the most direct use of this standard is probable cause of an arrest, which is a standard that often comes up in situations like shoplifting. A police officer can build a case to arrest you not only based on what they observe personally but also on information given by other people, such as a store employee or witness.

Direct observation is the most obvious way of establishing probable cause. In case a police officer personally observes you hiding merchandise and then exiting the store without paying, he/she has all the facts to constitute a reasonable belief that you have engaged in the crime of petty theft (Penal Code 484(a)). If a crime is committed in the officer’s presence, it provides grounds for a lawful, warrantless arrest. The visual evidence is overwhelming and does satisfy the probable cause test.

However, not all arrests are made on an officer's direct observation. Police may also rely on credible witness information. For example, the sworn statement of a store's loss prevention officer trained to observe the presence of theft. This statement could explain how they captured you on surveillance footage selecting an item, putting it in a bag or on your body, and then carrying it out of all the points of sale without paying.

A sworn statement from a trained loss prevention officer carries weight because they are credible and professionally obligated to report theft. When a police officer is given this detailed report, they can have a solid basis of probable cause even when a person did not witness the act.

To further establish the case, an officer will aim to gather corroborating evidence. This means they will seek more information to prove the witness's claim. For example, the officer could find you in the area, and you may fit the description given by the loss prevention officer. There is a possibility that the officer who arrests you may discover the stolen goods in your possession, and video footage of the store will substantiate the description given by the loss prevention officer.

There is a possibility that the officer who arrests you may discover the stolen goods in your possession, and video footage of the store will substantiate the testimony of the witness later. The combination of witness statements, matching descriptions, and possession of stolen goods can establish probable cause. The facts alone may not be sufficient, but when taken together on the totality of the circumstances test, the facts may amount to a reasonable likelihood that you did commit the theft and warrant a legal arrest.

Example 4: Probable Cause and Vehicle Searches

The California rules of vehicle search offer a special and commonly misconstrued interpretation of the probable cause standard. Although a warrant is typically needed to search a personal area like a house, the law does not apply the same to vehicles. This is due to the automobile exception to the Fourth Amendment, which recognizes that cars are mobile and evidence could be moved or destroyed before a warrant is obtained. Consequently, when an officer has probable cause to suspect that your vehicle has proof of a crime, the officer can execute a warrantless search.

There are several common avenues through which police can form probable cause to search your vehicle. The simplest one is the plain view doctrine, in which the officer observes the contraband or indicators of a criminal act in a visible location through a legitimate distance. For example, when you are stopped because of a traffic violation and the law enforcement officer sees a bag of what seems to be an illegal substance, a gun, or burglary instruments in the back seat. That observation is sufficient to give probable cause to search the rest of your car.

A more nuanced, but equally valid, way police can establish probable cause is through the plain smell doctrine. It may depend on the peculiar smell of some drugs, for example, roasted or uncooked marijuana. However, with the legalization of recreational cannabis in California, the law on this has become more complex. Since recreational cannabis is legal in California, marijuana odor alone is generally not sufficient to justify a vehicle search. Nevertheless, if the smell of burnt marijuana is accompanied by other signs of impairment, like red, bloodshot eyes, slurred speech, or driving under the influence, the combination of both may result in probable cause. This allows for a DUI investigation and the search to follow. Similarly, the odor of smoking marijuana and a minor in the vehicle would provide the police with probable cause to search, since it is unlawful for minors under the age of 21.

Your own admission can provide the probable cause to search your car. In a legitimate traffic stop, when you confess to the police officer that you have an illegal item inside the vehicle, for example, saying, “Officer, I have marijuana in my glove compartment,” or “I have a gun under the seat,” you have given the required probable cause. A simple statement as a direct acknowledgement of the presence of contraband will be sufficient in most cases to justify a complete search of the vehicle.

In all these situations, the officer's actions should be driven by objective facts, not a hunch, and ensure that the search remains a constitutionally reasonable exercise of authority.

The Exclusionary Rule and the Fruit of the Poisonous Tree

Without probable cause, a law enforcement act, for example, a search or an arrest, will not allow any evidence gathered to be used in court. This is because of an important law, the exclusionary rule.

The exclusionary rule is one of the main safeguards of your Fourth Amendment rights. According to it, any evidence obtained after an illegal search or seizure, that is, one conducted without probable cause or a legitimate warrant, should not be allowed in your criminal trial. This rule discourages police misconduct because it helps them eliminate the desire to abuse their constitutional rights. Given that they know that the illegally acquired evidence cannot be used to secure a conviction, they will be less tempted to obtain it illegally.

This rule extends beyond the initially tainted evidence through the "fruit of the poisonous tree" doctrine. This doctrine also treats evidence derived from an illegal search as inadmissible. For example, suppose that the police have illegally searched your automobile and that they have discovered a note indicating the address of a drug stash house. Any drugs discovered at that address would also be inadmissible in court. The stolen note is the so-called poisonous tree, and the drugs are the fruit of the tree. Both are legally invalid.

How a Motion to Suppress Can Lead to a Case Dismissal

When a law enforcement officer does not have probable cause, no evidence found as a consequence of the action can be used in court. This is because of a critical law concept called the exclusionary rule. To make these protections effective, your defense attorney must submit a formal request to the court, a Motion to Suppress Evidence as defined in California Penal Code 1538.5.

This is a necessary motion that allows your attorney to challenge the legality of the police actions. It requests a judge to consider the facts of the arrest or search and, in case the court does not find probable cause, to direct the suppression of the illegally obtained evidence. An effective motion to suppress can be a significant blow against the prosecution, since it could lead to the dismissal of the charges or a more advantageous plea bargain.

The Motion to Suppress is a pre-trial procedure that serves as a critical check on police power, ensuring that your constitutional rights are upheld before a trial begins. Usually, it is carried out through a formal hearing, during which your attorney will submit a written argument explaining why the evidence was gained unlawfully.

The prosecution is then given a chance to introduce its witnesses, the arresting officers, to justify their actions. The judge hears all the evidence and arguments and decides whether the evidence can be used. This hearing is a good chance to question the version of the police and to show the inconsistency of the statements of the police, which is a beneficial strategy even if the motion is ultimately denied.

Find a Criminal Defense Lawyer Near Me

Probable cause is one of the most critical principles in California law, ensuring that police act on solid, objective facts rather than mere suspicions. From a DUI stop to a search warrant for your property, this standard is the legal line that protects you from unreasonable government intrusion. If you believe your rights were infringed upon, and the police did not act with probable cause, the evidence against you can be questioned. Do not allow illegally obtained evidence to be used against you in court.

Talk to experienced criminal defense attorneys at Los Angeles Criminal Lawyer if you believe your rights were violated. Contact us at 310-502-1314 to discuss your case and fight for your rights.