In Bartkus v. United States, 359 U.S. 121 (1959), however, the Supreme Court implicitly suggested an exception to the dual sovereignty doctrine. Illinois had brought a robbery charge against a man who had been acquitted of the same charge in federal court. The Court upheld the state prosecution, but emphasized that the evidence failed to show that Illinois, in bringing its suit, had been "merely a tool of the federal authorities" or that its prosecution had been "a sham and a cover for a federal prosecution." Id. at 123-24.