Probable Cause

Probable Cause The Fourth Amendment to the U.S. Constitution stipulates that “no [search or arrest] warrants shall issue, but upon probable cause.” The amendment stemmed from colonial objections to the British abuse of general warrants and writs of assistance, legal documents that allowed officers to search and arrest individuals on mere suspicion of smuggling. The framers did not define the meaning of this phrase, although they clearly intended it to prevent the central government from arbitrarily intruding upon personal privacy.

The Fourth Amendment has been among the most heavily litigated of all the Bill of Rights, but the Supreme Court has considered the probable cause requirement in a relatively small number of cases. The Court measures probable cause by the test of reasonableness, a necessarily subjective standard that falls between mere suspicion and certain knowledge. Facts and circumstances leading to an arrest or seizure must be sufficient to persuade a reasonable person that an illegal act has been or is being committed. Always the test involves the consideration of a particular suspicion and a specific set of facts. Hunches or generalized suspicions are not reasonable grounds for concluding that probable cause exists. Judges, not law officers, must determine if probable cause exists, and thus if a warrant should be issued.

In 1968 the Court modified this standard to allow police officers to stop and frisk suspects in order to protect themselves, even without probable cause for arrest (Terry v. Ohio). More recently, the Court has accepted a law officer's experience, a suspect's reputation, and even anonymous tips, when buttressed by other facts, to weigh in the test of reasonableness when determining probable cause.

See also Search Warrant Rules, Exceptions to.

David J. Bodenhamer