In Feldman v. United States, 1943, the Supreme Court ruled on a case involving the admissibility of evidence obtained through wiretapping by federal agents. The defendant, Louis Feldman was convicted for conspiracy to defraud the United States and evade taxes based on evidence gathered from wiretapped phone conversations. He appealed his conviction arguing that this violated his Fourth Amendment rights against unreasonable searches and seizures as well as his Fifth Amendment right against self-incrimination. The court upheld Feldman's conviction in a 4-3 decision stating that while it is illegal for federal agents to tap wires under Federal Communications Act of 1934, such illegality does not render the resulting evidence inadmissible at trial if relevant and otherwise competent. It also held that since there was no coercion involved in obtaining these statements over telephone calls made voluntarily by him; hence they did not violate his Fifth Amendment rights either. This ruling significantly impacted future cases related to privacy laws and surveillance practices until it was later overturned by Katz v. United States (1967), which established an individual's right to privacy even when using public facilities like telephone booths.

In the dissenting opinion for Feldman v. United States, Justice Frank Murphy argued that the use of evidence obtained through wiretapping violated the Fourth Amendment's protection against unreasonable searches and seizures. He contended that such practices were invasive and contrary to principles of privacy and dignity. Furthermore, he believed it was inappropriate for courts to sanction this type of behavior by admitting wiretap evidence in trials. He also expressed concern about potential abuses if law enforcement agencies were allowed to continue using these methods without restrictions or oversight from courts or legislatures.