United States v. Grant 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 at trial was obtained through an illegal search and seizure. The Court held that the evidence was inadmissible and that the defendant could not be convicted. The case arose when the defendant, Grant, was arrested for possession of a firearm without a license. The arresting officers had conducted a search of Grant's home without a warrant, which was in violation of the Fourth Amendment. At trial, the prosecution sought to introduce the evidence obtained during the search as evidence of Grant's guilt. The Supreme Court held that the evidence obtained during the illegal search was inadmissible and that Grant could not be convicted on the basis of it. The Court reasoned that the exclusionary rule, which prohibits the use of illegally obtained evidence in criminal trials, was necessary to protect the Fourth Amendment rights of individuals. The Court also noted that the exclusionary rule was a necessary deterrent to police misconduct. In conclusion, the Supreme Court held that the evidence obtained during the illegal search of Grant's home was inadmissible and that Grant could not be convicted on the basis of it. The Court's decision established the exclusionary rule as a necessary protection of Fourth Amendment rights and a deterrent to police misconduct.

In United States v. Grant, the Supreme Court was tasked with deciding whether a defendant who had been convicted of an offense in a state court could be tried again for the same crime in federal court. The majority opinion held that such double jeopardy did not apply because the two courts were separate sovereigns and thus each had its own right to prosecute crimes committed within their respective jurisdictions. Justice Field dissented from this ruling, arguing that allowing multiple prosecutions by different governments violated fundamental principles of justice and fairness as well as constitutional protections against double jeopardy enshrined in both the Fifth Amendment and Article IV Section 2 Clause 1 of the Constitution. He argued that it would lead to oppressive practices where defendants could be subjected to repeated trials for one offense until they were found guilty or exhausted all legal remedies available to them. Furthermore, he noted that there was no precedent supporting such dual sovereignty doctrine since prior cases involving similar issues had always been decided on other grounds rather than relying upon this concept alone