McMurray et al. v. Brown was a United States Supreme Court case that dealt with the issue of whether a state court had the authority to issue a writ of mandamus to a federal court. The case involved a dispute between two parties, McMurray and Brown, over a contract for the sale of a steamboat. McMurray had sued Brown in a federal court, but the case was dismissed due to a lack of jurisdiction. McMurray then sought to have the state court issue a writ of mandamus to the federal court, ordering it to hear the case. The Supreme Court held that the state court did not have the authority to issue such a writ, as it would be in violation of the Supremacy Clause of the United States Constitution. The Court also held that the state court could not interfere with the proceedings of a federal court, as this would be a violation of the separation of powers doctrine. The Court ultimately held that the state court did not have the authority to issue a writ of mandamus to the federal court.

Justice Field delivered the dissenting opinion in McMurray et al. v. Brown, arguing that the majority's decision was wrongfully based on a misinterpretation of California law and an incorrect application of federal jurisdiction over state court decisions. He argued that under California law, a judgment creditor had no right to levy upon property held by another person unless they were able to prove their claim against the debtor beyond reasonable doubt; this was not done in this case as there was insufficient evidence presented at trial to support such a finding. Furthermore, Justice Field argued that it would be improper for the Supreme Court to review and reverse a state court decision without first determining whether or not there had been any error committed by said court during its proceedings - something which he believed had not occurred here due to lack of sufficient proof being provided at trial. As such, he concluded his dissent with an assertion that if Congress intended for federal courts to have authority over state judgments then it should pass legislation explicitly granting them such power rather than relying on judicial interpretation alone.