United States v. Cook was a United States Supreme Court case that dealt with the issue of whether a person 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 Cook who was accused of stealing a horse. The evidence used to convict him was obtained through a search of his home without a warrant. The Supreme Court ruled that the evidence was inadmissible and that Cook could not be convicted on the basis of it. The Court held that the Fourth Amendment of the United States Constitution protects citizens from unreasonable searches and seizures and that any evidence obtained through an illegal search and seizure is inadmissible in court. This ruling established the precedent that evidence obtained through an illegal search and seizure is inadmissible in court and that citizens are protected from unreasonable searches and seizures.

In United States v. Cook, the Supreme Court was tasked with deciding whether a man convicted of manslaughter in an Indian Territory court had been denied his constitutional right to a jury trial. The majority opinion held that since Congress had not extended the Sixth Amendment's guarantee of jury trials to Indian Territories, no such right existed and thus Cook could be lawfully tried without one. In dissent, Justice Field argued that all persons within U.S jurisdiction were entitled to due process under the Fifth Amendment regardless of where they lived or what their race was; as such he believed it unconstitutional for Congress to deny individuals living in Indian territories access to certain rights enjoyed by those elsewhere in America simply because they were Native Americans. He further noted that if this decision stood then any other group similarly situated would also be deprived of their basic constitutional rights and protections which should never happen in a country founded on principles of equality before the law for all citizens alike