In United States criminal law, probable cause is the legal standard by which police authorities have reason to obtain a warrant for the arrest of a suspected criminal and for a court's issuing of a search warrant. One definition of the standard derives from the U.S. Supreme Court decision in the case of Beck v. Ohio (1964), that probable cause exists when "at [the moment of arrest] the facts and circumstances within [the] knowledge [of the police], and of which they had reasonably trustworthy information, [are] sufficient to warrant a prudent [person] in believing that [a suspect] had committed or was committing an offense." Moreover, the grand jury uses the probable cause standard to determine whether or not to issue a criminal indictment. The principle behind the probable cause standard is to limit the power of authorities to conduct unlawful search and seizure of person and property, and to promote formal, forensic procedures for gathering lawful evidence for the prosecution of the arrested criminal. In the case of Berger v. New York (1967), the Supreme Court said that the purpose of the probable-cause requirement of the Fourth Amendment is to keep the state out of Constitutionally protected areas until the state has reason to believe that a specific crime is being committed or has been committed. The term of criminal law, the probable cause standard is stipulated in the text of the Fourth Amendment to the U.S. Constitution:
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. Moreover, in U.S. immigration law, the term "reason to believe" is equivalent to the probable cause standard of criminal law, and should not be confused with reasonable suspicion, which is the legal criterion required to perform a Terry stop in the U.S.
Definition The usual definition of the probable cause standard includes "a reasonable amount of suspicion, supported by circumstances sufficiently strong to justify a prudent and cautious person's belief that certain facts are probably true." Notably, this definition does not require that the person making the recognition must hold a public office or have public authority, which allows the citizenry's common-sense understanding of the legal standard of probable cause for arrest. Regarding the issuance of a warrant for arrest, probable cause is the "information sufficient to warrant a prudent person's belief that the wanted individual had committed a crime (for an arrest warrant) or that evidence of a crime or contraband would be found in a search (for a search warrant)". As a legal standard, probable cause is stronger than reasonable suspicion, but weaker than the requirement of evidence to secure a criminal conviction. Moreover, according to the Aguilar–Spinelli test a criminal court can choose to accept hearsay as a source of probable cause if the source-person is of reliable character or if other evidence supports the hearsay. In the case of Brinegar v. United States (1949), the Supreme Court defined probable cause as "where the facts and [the] circumstances within the officers' knowledge, and of which they have reasonably trustworthy information, are sufficient, in themselves, to warrant a belief, by a man of reasonable caution, that a crime is being committed."
History and development
The use of probable cause in the United States and its integration in the Fourth Amendment has roots in English common law and the old saying that "a man's home is his castle". This is the idea that someone has the right to defend their "castle" or home from unwanted "attacks" or intrusion. In the 1600s, this saying started to apply legally to landowners to protect them from casual searches from government officials. In the 1700s, the British use of the writs of assistance and general warrants, which allowed authorities to search wherever and whenever sometimes, without expiration date, in the American colonies were raised in several court cases. The first was in Massachusetts in 1761 when a customs agent submitted for a new writ of assistance and Boston merchants challenged its legality. In the case the lawyer for the merchants James Otis argued that writs of assistance violated the fundamentals of English Law and was unconstitutional. John Adams, a lawyer at the time who later wrote the Massachusetts provision on which the Fourth Amendment heavily relied, was impacted by James Otis's argument. A case against general warrants was the English case Entick v. Carrington (1765). In that case, Lord Camden the chief judge said that general warrants were not the same as specific warrants and that parliament or case law could not authorize general warrants. Along with these statements, Lord Camden also affirmed that the needs of the state were more important than the individual's rights. This upheld the ideology of the social contract while holding to idea that the government purpose was to protect the property of the people. He called for the government to seek reasonable means in order to search private property, as well as a cause.
Probationers and parolees In early cases in the United States, the Supreme Court held that when a person is on probation, the standard required for a search to be lawful is lowered from "probable cause" to "reasonable grounds" or "reasonable suspicion". Specifically, the degree of individualized suspicion required of a search was a determination of when there is a sufficiently high probability that criminal conduct is occurring to make the intrusion on the individual's privacy interest reasonable. The Supreme Court held in United States v. Knights:
Although the Fourth Amendment ordinarily requires the degree of probability embodied in the term "probable cause," a lesser degree satisfies the Constitution when the balance of governmental and private interests makes such a standard reasonable ... When an officer has reasonable suspicion that a probationer subject to a search condition is engaged in criminal activity, there is enough likelihood that criminal conduct is occurring that an intrusion on the probationer's significantly diminished privacy interests is reasonable. Later, in Samson v. California, the Supreme Court ruled that reasonable suspicion is not even necessary:
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