Probable cause

SIGNIFICANCE: Probable cause is the standard of proof necessary for law-enforcement officers to make arrests or to search and seize the belongings of suspects.

The Fourth Amendment to the US Constitution laid down the principle protecting people from unreasonable searches and seizures that forbids arresting officers from conducting these procedures without probable cause. The Framers of the Bill of Rights were concerned about government intrusions into the lives of citizens, and through the Fourth Amendment they sought to ensure that individual privacy would be respected.

The question as to what constitutes probable cause has been considered a number of times by the US Supreme Court. In 1949, in deciding the case of Brinegar v. United States, the Court stated, “probable cause is the facts and circumstances within the officers’ knowledge and of which they had reasonably trustworthy information and are sufficient in themselves to warrant a man of reasonable caution in the belief that an offense has been or is being committed.” This requires that the officer or agent of the government be fairly certain (to have some tangible proof, even if it is not admissible in court) before making an arrest or search or before making application for a warrant.

Probable cause, as a standard of proof, may best be considered as lying on a continuum with mere suspicion at one end and absolute certainty at the other end. Courts have held that reasonable suspicion, a level of proof somewhat lower than probable cause, is needed to stop and frisk suspects. On the scale somewhat higher than probable cause is preponderance of evidence, which is the standard of proof necessary to determine liability in civil cases.

Observational and Informational Probable Cause

There are two basic ways probable cause can be developed: through observation and information. Observational probable cause is formulated by police officers by using their five senses. If they can see, hear, smell, taste, or touch evidence that a crime has been or is being committed, an arrest or a search may be made. When determining the sufficiency of observational probable cause, courts take into consideration police officers’ training and experience. Thus, a police officer trained to detect the scent of marijuana is recognized as being able to distinguish that odor to develop probable cause, even if an ordinary citizen may not make that distinction. With observational probable cause the “totality of circumstances” standard is often used by the courts. With this standard, surveillance and other observations over time are compounded to determine whether probable cause exists. Informational probable cause is usually developed through investigations that yield certain facts about suspects. Included here are statements given by witnesses to crimes, victims’ statements, and statements given by other police officers and informants. Although probable cause is always required to arrest or search, warrants are not always necessary.

Warrantless Searches

It is clear from the language of the Fourth Amendment that the Founding Fathers intended for agents of the state to produce warrants prior to searching or arresting citizens. However, the courts have recognized the impracticality of that requirement in modern society. As early as 1925 a challenge to the need for officers to actually produce a physical document (warrant) was made by a man named Carroll whose car was searched during Prohibition. After government agents seized illegal liquor from his vehicle, Carroll appealed his conviction, alleging that the search was unconstitutional because the agents had no warrant. The US Supreme Court, in deciding for the government in Carroll v. United States, reasoned that automobiles can be moved before a warrant can be obtained and that the police need flexibility when probable cause exists.

A lesser standard of proof, reasonable suspicion, is needed by police officers before officers may stop a car. Once the car is stopped, probable cause for a full search may be developed by the circumstances. For example, a police officer may stop a car because it is weaving and, while talking to the driver, may smell alcohol. Although the weaving was not probable cause to search the car (it was reasonable suspicion to stop the car), the smell of alcohol provides the officer with probable cause to search. The US Supreme Court has ruled in Ross v. United States (1982) that once probable cause to search a vehicle has been established, the police have the right to search the entire vehicle, including all containers therein.

The probable cause requirement for police to conduct a valid search can be waived if the party consents to the search. The consent must be voluntary and intelligently given. Evidence seized without consent or probable cause is subject to exclusion from criminal proceedings pursuant to the exclusionary rule.

Reasonable Expectation of Privacy

Although the Fourth Amendment protects people and not places, not every location is protected by the language of the Fourth Amendment. The US Supreme Court has determined that the requirement for probable cause is restricted to areas in which there is a reasonable expectation of privacy. Evidence or contraband that is in plain view of a police officer is subject to seizure without probable cause. Likewise, if marijuana is grown in an open field behind one’s home, no reasonable expectation of privacy exists. The courts have held that persons have a reasonable expectation of privacy in a closed public phone booth but that they do not have a reasonable expectation of privacy while being detained in the rear seat of a police car. Issues related to the expectation of privacy have often generated controversy as increasingly advanced surveillance techniques have been developed.

Although police officers are the most likely criminal justice practitioners to develop probable cause, an independent tribunal (a judge or magistrate) must verify probable cause prior to the issuance of a search warrant or arrest warrant. The police officer applying for a search or arrest warrant must outline the probable cause in an affidavit, and the judge or magistrate must decide if the evidence is sufficient to support the warrant. As a systemic check, a probable cause hearing is held during the pretrial stage after an arrest so that a judge can ensure that probable cause exists. If it does not exist, the defendant must be released.

Bibliography

Bowers, John. "Probable Cause, Constitutional Reasonableness, and the Unrecognized Point of a 'Pointless Indignity.'" Stanford Law Review 66.5 (2014): 987–1055. Print.

Del Carmen, Rolando V. Criminal Procedure: Law and Practice,10th ed. Cengage, 2016. Print.

Hall, Daniel. Survey of Criminal Law. 2nd ed. Albany: Delmar, 1997. Print.

Hall, John Wesley. Search and Seizure. 3rd ed. Charlottesville: LEXIS Law, 2000. Print.

"Probable Cause." Cornell Law School, March 2024, www.law.cornell.edu/wex/probable‗cause. Accessed 9 July 2024.

Wallace, Harvey, and Cliff Robertson. Principles of Criminal Law, 6th ed. Pearson, 2015. Print.