Final answer:
Probable cause is met when there are sufficient facts and circumstances to lead a person of reasonable caution to believe a crime has been or is being committed. This legal threshold is essential for lawful arrests, searches, and the issuance of warrants, ensuring protection against unreasonable searches and seizures under the Fourth Amendment.
Step-by-step explanation:
Probable cause exists when the facts and circumstances within the officers' knowledge and of which they had reasonable trustworthy information are sufficient in themselves to warrant a man of reasonable caution in the belief that an offense has been or is being committed. This concept is a fundamental criterion in the legal system for determining the legality of a search or seizure by law enforcement officers or when issuing an arrest or search warrant.
For example, in the case of Terry v. Ohio, the Supreme Court ruled that the police may stop a person if they have a reasonable suspicion that the person has committed or is about to commit a crime, and they can frisk the suspect for weapons if they have a reasonable suspicion that the suspect is armed and dangerous, without violating the Fourth Amendment. This amendment specifically protects individuals from unreasonable searches and seizures and stipulates that no warrants shall issue without probable cause.
The standard of probable cause does not require evidence sufficient to secure a conviction but requires more than mere suspicion. Illinois v. Gates established the "totality of circumstances" test for determining probable cause, indicating that the decision must be made considering all the factors and information available to officers at the time.