McStay et al. v. Friedman was a United States Supreme Court case that dealt with the issue of whether a contract between two parties was valid. The case involved a dispute between two parties, McStay and Friedman, over a contract for the sale of a piece of land. McStay had agreed to purchase the land from Friedman for a certain sum of money, but Friedman refused to accept the payment and instead demanded a higher price. McStay then sued Friedman for breach of contract. The Supreme Court held that the contract between the two parties was valid and enforceable. The Court found that the contract was supported by consideration, meaning that both parties had given something of value in exchange for the other's promise. The Court also found that the contract was not void for lack of consideration, as Friedman had argued. The Court held that the contract was binding and enforceable, and that Friedman was liable for breach of contract. In conclusion, the Supreme Court held that the contract between McStay and Friedman was valid and enforceable, and that Friedman was liable for breach of contract. The Court's decision established that contracts must be supported by consideration in order to be valid and enforceable.

In McStay et al. v. Friedman, the Supreme Court was tasked with deciding whether a judgment in favor of the plaintiff should be reversed due to an error in admitting evidence during trial. The majority opinion held that the lower court's decision should stand and that any errors made were harmless and did not prejudice either party enough to warrant reversal of the judgment. Justice Field dissented from this ruling, arguing that it was improper for the lower court to admit certain testimony which had been excluded by another judge at a previous hearing on similar matters between these same parties. He argued that such admission constituted reversible error as it could have influenced or prejudiced one side over another, thus requiring reversal of the original judgment so as to ensure fairness and justice for all involved parties.