Boyd v. Moses was a United States Supreme Court case that was decided in 1868. The case involved a dispute between two parties over the ownership of a slave named Moses. The plaintiff, Boyd, claimed that he had purchased Moses from a third party and was the rightful owner. The defendant, Moses, argued that he was a free man and had never been a slave. The Supreme Court ultimately ruled in favor of Boyd, finding that the plaintiff had established a valid title to the slave. The Court held that the plaintiff had provided sufficient evidence to prove that he had purchased Moses from a third party and was the rightful owner. The Court also held that the defendant had failed to provide any evidence to support his claim that he was a free man. The decision in Boyd v. Moses established that a valid title to a slave could be established through the purchase of the slave from a third party. The case also established that a defendant could not simply claim to be a free man without providing any evidence to support the claim.

In the case of Boyd v. Moses, the Supreme Court was asked to consider whether a search warrant issued by an officer in one state could be enforced in another. The majority opinion held that it could not, as such warrants were only valid within their own jurisdiction and did not extend beyond its borders. However, Justice Field dissented from this ruling on the grounds that there is nothing in either federal or state law which prohibits officers from executing search warrants across state lines when necessary for public safety and justice. He argued that allowing such searches would help prevent criminals from evading prosecution by crossing into other states where they are out of reach of local authorities. Furthermore, he noted that if Congress had intended to limit searches to within each individual state's boundaries then it would have made this clear through legislation rather than leaving it up to judicial interpretation.