United States v. Hart 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 used to convict them was obtained through an illegal search and seizure. The case involved a man named William Hart, who was accused of stealing a horse from the United States government. The government searched Hart's home without a warrant and found the horse in his possession. Hart argued that the search was illegal and that the evidence should not be used against him. The Supreme Court ruled in favor of Hart, 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 government must obtain a warrant before conducting a search. The Court also held that the exclusionary rule applies to evidence obtained through illegal searches and seizures, meaning that such evidence cannot be used in court. This case established an important precedent in criminal law, as it established the exclusionary rule and affirmed the Fourth Amendment's protection against unreasonable searches and seizures. The ruling in this case has been cited in numerous subsequent cases, and it remains an important part of criminal law today.

In United States v. Hart, the Supreme Court was asked to decide whether a tax imposed on distilled spirits by Congress in 1862 was constitutional. The majority opinion held that it was, but Justice Field dissented from this decision and argued that the tax violated both the Fifth Amendment's prohibition against taking private property for public use without just compensation and Article I of the Constitution which grants Congress only limited powers over taxation. He reasoned that since distilling is an occupation protected by state law, any attempt to impose taxes upon it must be done with due regard for those laws or else would constitute a taking of private property without just compensation as prohibited by the Fifth Amendment. Furthermore, he argued that even if such taxes were permissible under some circumstances they could not be applied retroactively as had been done in this case because doing so would violate principles of fairness and justice established within our legal system.