What Is Probable Cause?

The probable cause requirement comes from the Fourth Amendment to the U.S. Constitution, which protects against unreasonable searches and seizures:

“The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.”

For a court to issue a warrant, there must be a showing of probable cause. Neither mere suspicion nor fair probability is enough.

This article provides a definition of probable cause. It also examines the probable cause standard in connection with the following:

• Detentions
• Arrests
• Searches
• Seizures
• Prosecutions

Understanding what probable cause is and what it requires can help you protect your rights.

Warrants and Probable Cause

To obtain a warrant, an officer will sign an affidavit. This states the facts the officer knows from their own observations. They can also base their affidavit on the observations of citizens or police informants.

These facts support their claim that probable cause exists to search, seize property, or arrest. The officer will then provide this information to a neutral judge or magistrate.

If a judge or magistrate finds probable cause based on the “totality of the circumstances,” they will issue an arrest or search warrant. The judge relies upon the honesty of the police officer in presenting accurate information. Federal courts have held that the judge may give considerable weight to a law enforcement officer’s conclusions regarding where evidence of a crime may be found in United States v. Mick (2001) and United States v. Caicedo (1996).

In addition, the Supreme Court adopted the “totality of the circumstances” test in Illinois v. Gates (1983). Law enforcement officials received an anonymous tip that a married couple was engaged in drug trafficking. Acting on this information, police ultimately obtained a search warrant. Police searched the couple’s residence and seized illegal drugs.

The couple moved to suppress the evidence seized, arguing that the probable cause cited was insufficient to support the warrant. The Supreme Court concluded the warrant was valid, noting that probable cause is a “fluid concept” that depends on law enforcement’s assessment of multiple factors.

Moreover, the Court wrote that probable cause cannot be confined to a “neat set of legal rules.” Instead, probable cause is essentially an “assessment of probabilities.”

Temporary Detention Does Not Require Probable Cause

Traffic stops and pedestrian questioning are examples of temporary detention. Temporary detention requires only reasonable suspicion, not probable cause.

If the police have reasonable suspicion, they act on specific facts and inferences about a particular person. It uses the “reasonable person” standard, which assesses whether a reasonable person would believe criminal activity was at hand and further investigation was required.

Detention can become a formal arrest if the detaining officer develops probable cause to believe a crime has been committed as a result of the investigation. For the detainee, the line between detention and arrest is not always clear. A criminal law attorney can help determine whether an arrest was lawful.

Probable Cause for Arrest

Probable cause for arrest exists when facts and circumstances known by the police officer would lead a reasonable person to believe that the suspect has committed, is committing, or is attempting to commit a criminal offense. The probable cause to arrest standard applies to both misdemeanor and felony offenses.

Police must base probable cause on objective facts. It can’t be based on a hunch. The requirements to establish probable cause are less than “a preponderance of the evidence,” the standard used to prove most civil cases in court, or “beyond a reasonable doubt,” the standard used in criminal cases.

Still, probable cause requires more than a reasonable suspicion. There must be articulable facts paired with a common-sense belief that a crime has been or is about to be committed. For instance, seeing someone loitering around a convenience store is not enough. If the person suddenly pulls on a mask and reaches into their pocket, it raises probable cause that they are about to rob the store.

When a police officer announces that a person is under arrest during a criminal investigation and places them in physical restraints, that is an arrest. At that moment, the arresting officer must have probable cause to believe the person committed a specific crime.

Someone arrested or charged without probable cause can file a civil lawsuit alleging false arrest or malicious prosecution. This type of suit will not succeed if the arresting officer is simply mistaken.

Probable Cause To Search Person or Property

Probable cause to search exists when facts and circumstances known to the law enforcement officer provide a reasonable person with grounds to believe that a crime was committed at the place to be searched or that evidence of a crime exists there. The police officer can then seek a search warrant from a judge or magistrate.

A search warrant authorizes an officer to conduct a limited search. Search warrants specify where law enforcement can search and items they can seize. Search warrants grant property owners Fourth Amendment rights to be secure in their “houses, papers, and effects.”

When a Search Warrant Is Not Needed

In some instances, police do not need a warrant to arrest or search. For example, if an officer witnesses a suspect commit a crime, they can make an arrest. If a warrantless arrest does occur, it may be subject to legal challenge by the defense in a subsequent proceeding. Circumstances that do not require a search or arrest warrant include the following:

• When the police have consent to search from a person who has use or control of the premises
• When conducting a search connected to a lawful arrest
• In an emergency that threatens public safety or the potential loss of evidence, also known as exigent circumstances
• If police impound a car after a DUI, and law enforcement takes inventory of the vehicle as part of standard procedure
• If contraband is “in plain view” from a location where the officer has a right to be present, such as next to a vehicle or at a front door
• Stop-and-frisk pat-downs for weapons, also known as a Terry stop

If a judge subsequently determines that a warrant is invalid or that a warrantless search was improper, the court will exclude the evidence or statements obtained. This is known as the exclusionary rule. At a suppression hearing, the judge decides whether the exclusionary rule applies to a particular piece of evidence. They hear testimony from the prosecuting and defense witnesses, along with case law analysis by the attorneys, to make their determination.

Probable Cause To Seize Property

Probable cause to seize property exists when facts and circumstances known to the officer would lead a reasonable person to believe that the item is contraband, is stolen, or constitutes evidence of a crime. With a search warrant, police are searching for the items described in the warrant. However, any contraband or evidence of other crimes they find may also be seized. For instance, if police execute a warrant to search a residence for drugs and find an illegal firearm during its execution, they can seize the weapon.

The police may not search outside the terms of the warrant. If the warrant allows a search for a stolen vehicle, the search must take place where a car could reasonably be concealed. Since a car probably would not be hidden in a drawer or under a bed, police may not search there. Anything they find in those locations would be excluded in a trial.

Probable Cause for Criminal Charges

The concept of probable cause extends to the prosecution of a criminal case. The Federal Rules of Criminal Procedure require a prosecutor to believe probable cause exists before recommending further investigation or prosecution. If the evidence tends to exclude a defendant or if the prosecutor knows it was obtained in violation of legal standard (“fruit of the poisonous tree”), then the prosecutor should not proceed with the case.

Get Legal Help With Your Probable Cause Questions

The Fourth Amendment protection against unreasonable search and seizure depends on probable cause. It is one of the most important legal protections against law enforcement overreach under criminal law, but also highly dependent on the facts of your case.

An experienced criminal defense attorney can provide valuable assistance in a criminal case. If you believe law enforcement performed an unlawful search and seizure, consider contacting an experienced criminal defense lawyer near you.