United States v. Rauscher is a United States Supreme Court case that dealt with the issue of whether a defendant could be convicted of a crime if the evidence used to convict them was obtained through an illegal search and seizure. The case involved a defendant, Rauscher, who was charged with receiving stolen goods. The evidence used to convict him was obtained through a search and seizure that was conducted without a warrant. The Supreme Court held that the evidence obtained through the illegal search and seizure was admissible in court and that Rauscher could be convicted of the crime. The Court reasoned that the exclusionary rule, which prohibits the use of illegally obtained evidence in court, did not apply in this case because the search and seizure was conducted in good faith and without any malicious intent. The Court also noted that the exclusionary rule was intended to deter police misconduct, not to punish innocent individuals. The Court's decision in United States v. Rauscher established that evidence obtained through an illegal search and seizure can be used in court if the search and seizure was conducted in good faith and without any malicious intent. This decision has been cited in numerous subsequent cases and has become an important precedent in the area of criminal law.

In United States v. Rauscher, the Supreme Court was tasked with determining whether a federal statute that prohibited certain types of securities transactions applied to an individual who had acted as a broker in such transactions before the passage of the law. The majority opinion held that it did apply and affirmed his conviction for violating the statute. Justice Field dissented from this decision, arguing that Congress could not retroactively punish individuals for actions taken prior to its enactment of legislation prohibiting those same actions. He argued further that if Congress were allowed to do so, then no one would be safe from prosecution since any action which became illegal after being committed could result in criminal liability regardless of when it occurred or what laws existed at the time it took place.