In Whiteley v. Warden, Wyoming State Penitentiary (1970), the U.S. Supreme Court ruled that an arrest warrant must be based on probable cause supported by oath or affirmation. The case involved a man named Harold Whiteley who was arrested for burglary based on a faulty warrant issued by local law enforcement in Laramie, Wyoming. The police had obtained the warrant using information from an unidentified informant without independently verifying its accuracy and reliability - thus failing to establish probable cause as required under the Fourth Amendment of the Constitution which protects against unreasonable searches and seizures. In a 7-2 decision, with Justice Hugo Black delivering the opinion of the court, it was held that since there were no supporting facts accompanying this complaint to justify issuing such a warrant, any evidence gathered after his arrest should have been excluded at trial because it violated Whitely's constitutional rights.

In the dissenting opinion for Whiteley v. Warden, Wyoming State Penitentiary, Justice Black argued that the majority's decision to overturn Whiteley's conviction on Fourth Amendment grounds was incorrect. He contended that there was sufficient information in the arrest warrant and accompanying affidavit to establish probable cause for his arrest. The fact that some of this information came from an unidentified informant did not negate its value or reliability in establishing probable cause as long as it was corroborated by other facts within law enforcement’s knowledge. Furthermore, he disagreed with the majority's view that a police officer cannot rely on a warrant issued by a magistrate if it is later determined to be unsupported by probable cause; such an approach would undermine faith in judicial decisions and place undue burdens on law enforcement officers who are often required to make quick judgments under pressure.