19 Sep 25
Probable cause is a fundamental principle of the Fourth Amendment of the U.S. Constitution, protecting citizens against unreasonable searches and seizures. It is the test that the police must pass before they can search, seize property, and make an arrest.
Probable cause is a reasonable belief, supported by facts and circumstances, that a crime has occurred or that crime evidence can be found at a specific location. It is more than the standard of mere suspicion, but it is not as rigorous as the evidence needed to convict.
Without this significant legal yardstick, police conduct would be arbitrary and breach an individual’s privacy and liberty rights. Learning about the scope and application of probable cause is crucial to understanding the balance between individual rights and public safety in California.
Probable Cause and Reasonable Suspicion
Probable cause is a legal standard that requires a reasonable belief, based on specific facts, that a crime has been committed or that evidence of a crime is present in a particular place. It is a greater level than reasonable suspicion and is typically needed to justify arrests and searches under the Fourth Amendment of the United States Constitution.
The standard is not about absolute certainty. It is about whether the facts in hand would cause a reasonable person to believe that an illegal act has been committed. Although both are legal requirements that law enforcement uses, they vary in certainty and the actions they warrant. Think of them as steps on a staircase, with reasonable suspicion being the lower step.
- Reasonable suspicion—This is a lesser standard based on specific, articulable facts that, in conjunction with reasonable inferences, indicate that a person is engaged in a crime. It is the excuse to justify a brief, temporary investigatory stop, also known as a “Terry stop,” and a pat-down of a person’s outer clothing to check for weapons. It does not need evidence of a crime, only suspicion. For example, an officer would notice someone peeking into a car window, often late at night in a high-crime area. This may be a sufficient reason to stop and ask questions briefly.
- Probable cause—This is a greater standard that cannot be based on a hunch. It requires facts and circumstances, which would lead a reasonable person to believe that a crime has been committed. This threshold must be met to make an officer effect a lawful arrest or obtain a search warrant. For example, if an officer smells a strong odor of marijuana in a car, the smell, along with other circumstances, may be enough to provide probable cause to enter the vehicle to search it and find illegal drugs. This is because the smell can give a reasonable suspicion that a crime (possession of an illegal substance) is being committed.
The crucial difference lies in the actions each standard justifies. Reasonable suspicion allows a brief detention and pat-down. In contrast, probable cause allows more substantial intrusions, including a full search or arrest. The Fourth Amendment guarantees a citizen against unreasonable searches and seizures, and these two terms are the legal standards applied to define whether a particular action of the police was reasonable or not.
According to the Fourth Amendment, no warrants are to be issued without probable cause, which must be supported by oath or affirmation, and the place to be searched and persons or property to be taken must be specified. This shows that a warrant is the main instrument of a legal search and should be founded on probable cause. The reason is to safeguard people against unreasonable government intrusion. Probable cause is necessary because law enforcement cannot search or arrest at will.
Although officers are sometimes allowed to act without a warrant when the exceptions to the warrant requirement are present, they still, in most cases, need to demonstrate the probable cause standard.
Let us look at examples where probable cause applies.
Example 1: The Traffic Stop That Leads to a Vehicle Search
A traffic stop by its very nature is a temporary detention that is founded on reasonable suspicion. An officer notices a vehicle code violation, like speeding or a broken taillight, and has a legal justification to pull the car over. However, this initial reasonable suspicion in stopping the vehicle does not automatically give the officer the right to search the car. To do that, the officer must meet a greater legal burden, probable cause.
In California, this progression of reasonable suspicion to probable cause frequently occurs through a legal concept referred to as the plain view doctrine or, in the case of odors, the plain smell doctrine. These are the exceptions to the warrant requirement of the Fourth Amendment. The plain view doctrine allows an officer to conduct a warrantless seizure of evidence, provided that three requirements are satisfied:
- The officer is in a legal position to view the item
- The object is in plain sight
- The incriminating nature of the object is apparent
For example, when an officer is conducting a lawful traffic stop and, upon approaching the vehicle, he/she notices a bag of cocaine that is sitting on the passenger seat. The bag is an immediately incriminating object in plain view, and the officer has probable cause. The officer is then entitled to search the car further for additional evidence of that crime. This is because the visual evidence provides the necessary fair probability that a crime has occurred and that further evidence of that crime is in the vehicle.
Likewise, California’s plain smell doctrine is another probable cause source. Although the legalization of recreational marijuana in California has made this difficult, the odor of burnt marijuana in a car can still serve as probable cause to search the vehicle. The smell suggests a violation of the law against driving under the influence or having an open container in the car. The odor of burning or unsealed marijuana, when taken together with other aspects, including erratic driving behavior or bloodshot eyes, can give a reasonable officer reason to suspect a crime is taking place.
It is noteworthy that the probable cause limits the scope of the search. When an officer has probable cause to search a vehicle for a weapon, he/she can search any area of the car where a gun might be hidden.
If the likely cause concerns drugs, they are allowed to search any receptacle or place where drugs could have a reasonable chance of being concealed, like the trunk or a locked glove box, without an additional warrant. This is because the automobile exception to the Fourth Amendment acknowledges that vehicles are mobile and evidence may be lost or destroyed as an officer works to secure a warrant.
Example 2: Arresting Lawfully Without a Warrant
In California, police officers may arrest without a warrant for a felony under these circumstances:
- When the felony is committed in their presence, or
- When they have probable cause to believe that a person has committed a felony, even though the crime was committed out of their presence.
This vital power enables officers to take swift action to prevent additional injury or the escape of a criminal.
When an officer is a direct eyewitness to a crime being committed, they have an immediate and undeniable cause to make a warrantless arrest. For example, when an officer is responding to a report of a disturbance in a public place and witnesses an individual beating another. The direct, first-hand knowledge of the felony offense of assault is enough probable cause to arrest the individual immediately. This firsthand observation is a conclusive fact that a crime has been committed, and the person has committed it.
Nevertheless, an officer is not required to witness the crime to make a lawful warrant arrest. Other sources can be used to develop probabilities of a felony arrest. For example, when a witness describes an individual who has just robbed someone and identifies the still-nearby robber. Based on this reliable information, the officer could conclude that the person committed the crime.
That is a critical difference, as a simple anonymous tip-off may not suffice, but a particular, credible eyewitness testimony can. The facts should be strong to the extent that a reasonable officer would think a person committed the felony.
The same principle is applicable in the case of misdemeanors, but there is one big difference. In California, a warrantless arrest for a misdemeanor can only be made when the offense was committed in the presence of the officer, with some exceptions, for example, in domestic violence and driving under the influence cases.
Example 3: Process of Obtaining a Search Warrant
The strongest shield against unreasonable searches is the search warrant, which involves a formal procedure based on probable cause. This process serves as an essential safeguard against police authority so that before the police can invade a person’s privacy, a neutral third party, a judge, examines evidence.
The process starts with collecting evidence by an officer or a law enforcement agent to create a case to justify a search. This evidence may encompass a broad spectrum of information, including witness statements, video surveillance footage, credible informant tips, and physical evidence at a crime scene. All this information is then summarized into a detailed document referred to as a probable cause affidavit by the officer.
The affidavit is presented to a judge. It is a legal and formal document that must show the facts and circumstances that cause the officer to believe that a crime has occurred and that evidence will be found at a particular place. There is no place for hunches or guesses; there must be a clear, compelling case with specific, verifiable facts to back it up. The more accurate and factual the information, the more solid the argument that it supports the probable cause.
After the affidavit is prepared, the officer takes it before a judge. The role of the judge is to be an impartial and objective magistrate. They are not merely a rubber stamp of law enforcement. They must review the affidavit separately to determine whether it contains sufficient information to support the probable cause. The judge has to be satisfied that there is a fair chance that the search will yield evidence of a crime. The judge could sign a search warrant if they are satisfied with the facts in the affidavit. This warrant gives officers the legal right to search a particular location and confiscate certain items.
This judicial review is a core aspect of the Fourth Amendment against unreasonable search. It ensures that the choice to intrude into an individual’s privacy is not left to the whims of the officer on the street. Instead, it is made by a judicial figure based upon a calm and objective consideration of the facts.
Example 4: The Preliminary Hearing in a Felony Case
A preliminary hearing is a significant legal event between an arrest on a felony and a trial. It aims to establish the existence of sufficient evidence to warrant a trial. This hearing is basically a probable cause hearing, which takes place in a courtroom. The prosecutor has to provide a judge with evidence that there is sufficient cause to believe that a felony has been committed and that the defendant is the one who has committed it.
The hearing is a significant milestone in the criminal justice process. The prosecution will usually present witnesses, who may be the arresting officer or a victim, to give evidence concerning the facts of the case. The defense attorney is not only supposed to listen; he/she can cross-examine these witnesses. This provides the defense with a golden opportunity to:
- Question the evidence presented by the prosecution
- Identify the weak points of their case and
- Possibly, get a clearer idea of the evidence used in the trial
The judge is a neutral arbiter who listens to testimony and examines the evidence. They do not decide on guilt or innocence, but only whether the degree of probable cause has been reached. Upon finding that the prosecution has provided sufficient evidence, the judge will hold the defendant to answer, and the case will be taken to trial.
However, if the judge concludes that the prosecutor has not satisfied the standard, he/she may do one of two things.
- They could disregard or diminish the charges to a misdemeanor if the evidence proves the minor crime.
- In other instances, the judge could dismiss the charges, and a defendant is set free if the evidence is too weak.
As described in California Penal Code 872, this process is an essential check against the state bringing felony charges without a reasonable foundation of evidence.
What Happens When Police Officers Operate Without Probable Cause
The Fourth Amendment is enforced by a powerful legal principle called the exclusionary rule. This rule is the main consequence of law enforcement not acting based on probable cause or a valid warrant. The rule states that the prosecution cannot use evidence gathered due to an unlawful search and seizure in a criminal trial. It is a means of discouraging police misconduct and ensuring law enforcement respects constitutional rights.
The exclusionary rule applies to all the evidence obtained due to the original unlawful violation in the fruit of the poisonous tree doctrine. Under this principle, not only is illegally obtained evidence inadmissible, but any additional evidence derived from it is also inadmissible.
For example, if police unlawfully enter a house and discover a stolen laptop, the laptop cannot be used as evidence. However, should the serial number on the laptop direct them to a warehouse of other stolen property, the property in the warehouse is also considered the fruit of a poisonous tree and inadmissible.
The practical use of these rules is a motion to suppress evidence. A motion to suppress is a request made by the defense attorney to the court to rule out the use of some evidence at trial because the evidence was obtained in a manner that violated the defendant’s Fourth Amendment rights. The defense should claim that the police did not have probable cause or a warrant.
When a judge grants the motion, the evidence is inadmissible in the trial. This can be a crushing blow to the prosecution’s case and could cause the prosecution to drop the charges, particularly in instances where the suppressed evidence is the primary evidence.
For example, in a drug case, the drugs could be suppressed. The case will probably be dismissed if the prosecution lacks evidence to proceed. The Exclusionary rule and the doctrines related to it are a crucial limitation on the power of the government, and they ensure that law enforcement is accountable for its actions and uphold the individual’s constitutional rights.
Find a Criminal Defense Attorney Near Me
Probable cause is the foundation of justice, a key principle that protects citizens from government excesses. It is the most crucial benchmark for any traffic stop that results in a vehicle search, a warrantless arrest, and the formal process of obtaining a warrant. When you experience an investigation or a criminal charge against you, a failure of law enforcement to meet this standard may be the key to your defense.
For those navigating the complexities of the legal system in Van Nuys, contact Leah Legal today to discuss your case and ensure your constitutional rights are protected. Contact us at 818-484-1100.
