Definition of probable cause
probable cause (uncountable)
- (US) The standard by which a police officer may make an arrest or conduct a personal or property search.
- In accident investigations, the conclusions reached by the investigating body as to the factor or factors which caused the accident.
In United States criminal law, probable cause refers to the standard by which a police officer has the authority to make an arrest, conduct a personal or property search, or to obtain a warrant for arrest. 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.
The most well-known definition of probable cause is "a reasonable belief that a person has committed a crime". Another 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".
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.
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.
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