Constitutional Protection

The legal requirement of probable cause is derived from the Fourth Amendment of the Unites States Constitution, which protects individuals from unreasonable searches and seizures.

Probable Cause Standard

Probable cause does not require absolute certainty that a crime has been committed. The amount of evidence sufficient to meet the probable cause standard is evidence from which a reasonable person could conclude that a suspect has committed or is in the process of committing a crime.

Supreme Court Case

In 1983, the United States Supreme Court clarified the probable cause standard required for arrests to pass constitutional muster. In Illinois v. Gates, the court ruled that a "substantial chance" or "fair probability" that criminal activity has transpired is sufficient to constitute probable cause for an arrest.

Warrant Not Required

Because in many circumstances it would be impractical for the police to obtain a warrant, securing a warrant is not a constitutional prerequisite for making an arrest.

Issueing A Warrant

The same probable cause standard is used as a basis for obtaining an arrest warrant from a judge.