Folger v. United States 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 man named Folger who was charged with the possession of counterfeit money. The evidence used to convict him was obtained through a search of his home without a warrant. The Supreme Court ruled in favor of Folger, holding that the evidence obtained through the illegal search and seizure was inadmissible in court. The Court reasoned that the Fourth Amendment of the United States Constitution protects citizens from unreasonable searches and seizures, and that the evidence obtained through the illegal search and seizure was in violation of this amendment. The Court also held that the exclusionary rule applied in this case, meaning that any evidence obtained through an illegal search and seizure was inadmissible in court. This case established the precedent that evidence obtained through an illegal search and seizure is inadmissible in court, and that the exclusionary rule applies in such cases. This ruling has been used in many subsequent cases to protect citizens from unreasonable searches and seizures.

In Folger v. United States, the Supreme Court was asked to decide whether a taxpayer could deduct from their income taxes certain expenses related to the sale of property that had been held for investment purposes. The majority opinion found that these expenses were not deductible because they did not arise out of trade or business activities and thus did not qualify as ordinary and necessary business expenses under existing tax law. Justice Field dissented, arguing that Congress intended for taxpayers to be able to deduct such costs when selling property held for investment purposes in order to prevent them from being unfairly taxed on profits which may have already been subject to taxation at some point during its ownership period. He argued further that if Congress had intended otherwise it would have explicitly stated so in the relevant statutes rather than leaving it up to judicial interpretation.