Probable Cause

What gives law enforcement the right to arrest someone? "Probable cause" is the legal basis that allows police to arrest someone, conduct a search, or seize property. This requirement comes from the Fourth Amendment to the U.S. Constitution, which states the following:

"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."

Thus, for a court to issue a warrant, it must be supported by a showing of probable cause.

This article provides a definition of probable cause. It will then examine the probable cause standard in connection with the following:

• Detentions
• Arrests
• Searches
• Seizures
• Prosecutions

Warrants and Probable Cause

To get a warrant, an officer will sign an affidavit. The affidavit 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 conduct a search, seize property, or make an arrest. The officer will then provide this information to a neutral judge or magistrate.

If a judge or magistrate agrees that probable cause exists based on the "totality of the circumstances," they will issue an arrest warrant 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 (United States v. Mick (2001); United States v. Caicedo (1996)). The accused is not present to rebut the claims.

The Supreme Court adopted the “totality of the circumstances" test in Illinois v. Gates (1983). There, 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. They argued probable cause did not support the warrant. The Supreme Court concluded the warrant was valid. The Court noted 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 the questioning of pedestrians 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. "Reasonable suspicion" uses the "reasonable person standard." Would a reasonable person 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 charge a crime as a result of the investigation. For the detainee, the line between detention and arrest is not always clear.

Probable Cause for Arrest

If, during a criminal investigation, a police officer announces that a person is under arrest 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.

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 cannot be based upon a hunch. The evidence required to show probable cause is less than "a preponderance of the evidence," which is the standard used to prove most civil cases in court. It is also less than “beyond a reasonable doubt," the standard used in criminal cases. However, probable cause requires more than "a reasonable suspicion."

Someone arrested or charged without probable cause could file a civil lawsuit. They could allege, for example, false arrest or malicious prosecution. However, 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 the basis for a reasonable person to believe that they committed a crime at the place to be searched or that evidence of a crime exists at the location.

The police officer can then seek a search warrant from a judge or magistrate. A search warrant gives the officer permission to conduct a limited search. Search warrants specify where law enforcement can search and items they can seize.

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 witnessed 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 sight" from a location where the officer has a right to be present (For example, outside the car door, at the front door of a house or apartment)

• Stop and frisk pat-downs for weapons

If a judge subsequently determines that a warrant is invalid, or a warrantless search is determined to have been improper, the court will exclude 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. The judge will 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.

When a search warrant is in effect, police generally search only for the items described in the warrant. However, any contraband or evidence of other crimes they come across may, for the most part, be seized as well.

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. Therefore, the prosecutor must believe that the person committed the crime before they recommend further investigation or prosecution.

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 in the criminal law system. However, it is 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.