The FBI obtained a search warrant and uncovered evidence that was ultimately used to convict William Spinelli (defendant) of illegal gambling. The affidavit primarily rested on information from a confidential informant, and the FBI was able to corroborate some of this information through its own investigation. Spinelli challenged the constitutionality of the warrant. The district court denied Spinelli's motion, holding he did not have standing to raise a Fourth Amendment claim. The court of appeals found that Spinelli did have standing and further held that the warrant was issued without probable cause. After a rehearing en banc, the court of appeals sustained the warrant and affirmed Spinelli's conviction. The United States Supreme Court granted certiorari to consider the validity of the search and seizure.