The examples and perspective in this article deal primarily with the United States and do not represent a worldwide view of the subject. Please improve this article and discuss the issue on the talk page. (February 2011)
In United States criminal law, probable cause (also referred to as reasonable cause) is the standard by which an officer or agent of the law has the grounds to obtain a warrant for, or as an exception to the warrant requirements for, making an arrest or conducting a personal or property search, etc. when criminal charges are being considered. It is also used to refer to the standard to which a grand jury believes that a crime has been committed. This term comes from the Fourth Amendment of the United States 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.
"Probable" in this case may relate to actual statistical probability, or to a general standard of common behavior and customs. The context of the word "probable" here is not exclusive to community standards and does not predate statistics, as some have suggested.
1 Definitions in the United States
1.1 Probationers and parolees,
1.2 Accident investigation,
2 Other countries,
3 Related cases,
4 Probable cause hearings,
5 See also,
7 External links,
Definitions in the United States:
A common definition is "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". Notable in this definition is a lack of requirement for public position or public authority of the individual making the recognition, allowing for use of the term by citizens and/or the general public.
In the context of warrants, the Oxford Companion to American Law defines probable cause as "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)". "Probable cause" is a stronger standard of evidence than a reasonable suspicion, but weaker than what is required to secure a criminal conviction. Even hearsay can supply probable cause if it is from a reliable source or supported by other evidence, according to the Aguilar-Spinelli test.
Probationers and parolees:
In early cases, 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, "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: "The California Legislature has concluded that, given the number of inmates the State paroles and its high recidivism rate, a requirement that searches be based on individualized suspicion would undermine the State's ability to effectively supervise parolees and protect the public from criminal acts by reoffenders. This conclusion makes eminent sense. Imposing a reasonable suspicion requirement, as urged by petitioner, would give parolees greater opportunity to anticipate searches and conceal criminality."
The court held that reasonableness, not individualized suspicion, is the touchstone of the Fourth Amendment. It has been proposed that Fourth Amendment rights be extended to probationers and parolees, but such proposals have not gained traction. There is not much that remains of the Fourth Amendment rights of probationers after waiving their right to be free from unreasonable searches and seizures. An essay called "They Released Me from My Cage...But They Still Keep Me Handcuffed" was written in response to the Samson decision.
It has been argued that the requirement that a police officer must have individualized suspicion before searching a parolee's person and home was long considered a foundational element of the Court's analysis of Fourth Amendment questions and that abandoning it in the name of crime prevention represents an unprecedented blow to individual liberties.
The term is used in accident investigation to describe the conclusions reached by the investigating body as to the factor or factors which caused the accident. This is primarily seen in reports on aircraft accidents, but the term is used for the conclusion of diverse types of transportation accidents investigated in the United States by the National Transportation Safety Board or its predecessor, the Civil Aeronautics Board.
In the criminal code of some European countries, notably Sweden, probable cause is a higher level of suspicion than "justifiable grounds" in a two level system of formal suspicion. The latter refers only to the suspect being able to and sometimes having a motive to commit the crime and in some cases witness accounts, whereas probable cause generally requires a higher degree of physical evidence and allows for longer periods of detention before trial. See häktning.
The Supreme Court decision Illinois v. Gates 462 U.S. 213 (1983) lowered the threshold of probable cause by ruling that a "substantial chance" or "fair probability" of criminal activity could establish probable cause. A better-than-even chance is not required.,
The decision in Terry v. Ohio, 392 U.S. 1 (1968) established that "stop and frisks" (seizures) may be made under reasonable suspicion if the officer believes a crime has been committed, is, or soon will be committed with a weapon concealed on such person.,
In United States v. Matlock, 415 U.S. 164 (1974), the Court announced the "co-occupant consent rule" which permitted one resident to consent in the co-occupant's absence. The case established that an officer who made a search with a reasonable belief that the search was consented to by a resident did not have to provide a probable cause for the search.,
However, in Georgia v. Randolph, 547 U.S. 103 (2006) the Supreme Court ruled, thus replacing Matlock, when officers are presented with a situation wherein two parties, each having authority to grant consent to search premises they share, but one objects over the other's consent, the officers must adhere to the wishes of the non-consenting party.
New Jersey v. T. L. O., 468 U.S. 1214 (1985) set a special precedent for searches of students at school. The Court ruled that school officials act as state officers when conducting searches, and do not require probable cause to search students' belongings, only reasonable suspicion.,
In O'Connor v. Ortega, 480 U.S. 709 (1987), the Court relied on T.L.O. to extend the reasonable suspicion standard to administrative searches of public employees' belongings or workplaces when conducted by supervisors seeking evidence of violations of workplace rules rather than criminal offenses.,
Probable cause hearings:
See also: Evidentiary hearing
In the various states of the United States, a probable cause hearing is the preliminary hearing typically taking place before arraignment and before a serious crime goes to trial. The judge is presented with the basis of the prosecution's case, and the defendant is afforded full right of cross-examination and the right to be represented by legal counsel. If the prosecution cannot make a case of probable cause, the court must dismiss the case against the accused.