United States v. Ulrici 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 defendant, Ulrici, was charged with receiving stolen goods that had been seized by federal agents without a warrant. The Supreme Court held that the evidence was admissible and that Ulrici could be convicted of the crime. The Court reasoned that the Fourth Amendment does not require that evidence obtained through an illegal search and seizure be excluded from trial. Rather, the Court held that the exclusionary rule only applies when the government has acted in bad faith or with reckless disregard for the rights of the accused. In this case, the Court found that the government had acted in good faith and that the evidence was properly obtained. Therefore, the Court held that the evidence was admissible and that Ulrici could be convicted of the crime. The Court's decision in United States v. Ulrici established that evidence obtained through an illegal search and seizure can be used in a criminal trial, provided that the government has acted in good faith. This decision has been cited in numerous subsequent cases and has become an important part of Fourth Amendment jurisprudence.

In United States v. Ulrici, the Supreme Court was tasked with determining whether a defendant could be convicted of aiding and abetting another person in committing an offense against the United States when that other person had already been acquitted of such an offense. The majority opinion held that since there was no conviction on which to base a charge of aiding and abetting, it would be impossible for the government to prove its case beyond a reasonable doubt. However, Justice Field dissented from this decision arguing that although acquittal may have prevented prosecution for one particular crime, it did not necessarily mean that all evidence related to any potential criminal activity should also be excluded from consideration by prosecutors. He argued further that if Congress intended to exclude such evidence then they would have explicitly stated so in their legislation; however they had not done so here and thus he believed it should still remain admissible as long as relevant facts were established through competent testimony or otherwise proved at trial.