A standard that the law enforcement agents must meet before performing a search or an arrest; or, for obtaining a search and/or an arrest warrant.  The Fourth Amendment to the United States Constitution specifically provides that, “[t]he 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.”

In the case of an arrest, the term “probable cause” has been defined as the amount of facts and circumstances within the police officer’s knowledge that would warrant a reasonable person to conclude that the specific individual arrested has committed a crime.  In the case of a search, the term “probable cause” has been defined as the amount of facts and circumstances within the police officer’s knowledge that would warrant a reasonable person to conclude that the specific items related to a crime (e.g., a weapon used to commit the crime or stolen property) will be found at the particular place to be searched.  Thus, the determination of whether probable cause exists entails an objection, not a subjective, analysis.

To establish probable cause, there must be facts (instead of mere conclusory assertions) that amount to more than a mere hunch or suspicion, but considerably less than proof beyond a reasonable doubt that is required to obtain a criminal conviction.  As Justice Black observed in his dissent in Spinelli v. United States, 393 U.S. 410 (1969), “Of course it would strengthen the probable-cause presentation if eyewitnesses could testify that they saw the defendant commit the crime . . . [However,] [n]othing in the Constitution . . . requires that the facts be established with that degree of certainty.”  Id. at 429.

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Probable cause may not be established simply by showing that the officer who made the challenged arrest or search subjectively believed he had grounds for his action.  As emphasized in Beck v. Ohio: ‘If subjective good faith alone were the test, the protection of the Fourth Amendment would evaporate, and the people would be “secure in their persons, houses, papers, and effects” only in the discretion of the police.’  The probable cause test, then, is an objective one; for there to be probable cause, the facts must be such as would warrant a belief by a reasonable man.

 Wayne R. LaFave & Jerold H. Israel, Criminal Procedure § 3.3, at 140 (2d ed. 1992).

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