Sweeney v. United States was a case heard by the United States Supreme Court in 1883. The case involved a dispute between the United States and John Sweeney, a former employee of the United States Treasury Department. Sweeney had been dismissed from his position for alleged misconduct and was seeking back pay for the time he had worked. The Supreme Court held that the United States was not liable for back pay to Sweeney. The Court reasoned that the United States had the right to dismiss an employee for misconduct without being liable for back pay. The Court also held that the United States was not liable for back pay because the misconduct of which Sweeney was accused was not proven. The Court's decision in Sweeney v. United States established that the United States is not liable for back pay to employees who are dismissed for misconduct. The decision also established that the United States is not liable for back pay if the misconduct of which the employee is accused is not proven.

Justice Field delivered the dissenting opinion in this case, arguing that the trial court had erred in its instructions to the jury. He argued that a conviction should not have been sustained on circumstantial evidence alone; rather, there must be some direct proof of guilt. In his view, it was insufficient for the prosecution to prove only that Sweeney had access to and knowledge of certain documents related to an alleged conspiracy without any other corroborating evidence linking him directly with criminal activity. Justice Field further noted that even if such circumstantial evidence were sufficient for a conviction, then at least one witness should have been called who could testify as having seen Sweeney commit or participate in acts which constituted part of the crime charged against him. As no such witness was presented by either side during trial proceedings, Justice Field concluded that there was not enough reliable proof available upon which a guilty verdict could be based and thus he dissented from the majority’s decision affirming Sweeney's conviction.