United States v. Crusell was a United States Supreme Court case that dealt with the issue of whether a defendant could be convicted of a crime if the evidence presented was obtained through an illegal search and seizure. The case involved a defendant, Crusell, who was charged with the possession of counterfeit coins. The coins were discovered during a search of Crusell's home, which was conducted without a warrant. Crusell argued that the evidence should be excluded from the trial because it was obtained through an illegal search and seizure. The Supreme Court held that the evidence was admissible and that Crusell could be convicted of the crime. The Court reasoned that the Fourth Amendment, which protects against unreasonable searches and seizures, does not provide a remedy for the exclusion of evidence obtained through an illegal search and seizure. The Court reasoned that the exclusionary rule, which prohibits the use of illegally obtained evidence, was not applicable in this case. The Court's decision in United States v. Crusell established that the exclusionary rule does not apply to criminal cases and that evidence obtained through an illegal search and seizure can be used to convict a defendant. This decision has been cited in numerous cases since then and has been used to support the idea that the exclusionary rule does not apply to criminal cases.

In United States v. Crusell, the Supreme Court was tasked with determining whether a defendant had been properly convicted of treason against the United States. The majority opinion held that since there was no evidence to suggest that Crusell had taken up arms or provided aid and comfort to an enemy of the state, he could not be found guilty under Article III of the Constitution. However, Justice Field dissented from this ruling on two grounds: firstly, he argued that Congress has broad authority in defining what constitutes treason; secondly, he asserted that even if it is assumed for argument's sake that Crusell did not take up arms or provide aid and comfort to an enemy of the state as defined by Article III, his actions still constituted “adhering” to enemies within its meaning – which would make him liable for conviction regardless. In conclusion then Justice Field believed Congress should have wide latitude in defining what constitutes treason and thus disagreed with his colleagues' decision in this case.