The correct option is "the prosecutor filed a Supreme Court case against Nixon."
In July 1973, thanks to the testimonies of former Nixon officials and staff, investigations conducted by the Watergate Committee of the United States Senate revealed that Nixon had a tape system in its offices and that many conversations had been recorded. After a series of legal battles, the Supreme Court of the United States ruled unanimously that the president should deliver the tapes to government investigators, which he finally agreed to. The recordings directly implicated Nixon in the case, revealing that he had tried to cover up the theft with "questionable chicanery." Due to the fact that with almost total probability, the president would have been subjected to an impeachment ("process of destitution") by the two chambers of the legislative power of the State, Nixon resigned as president on August 9, 1974. On August 8, September 1974, his successor, also Republican Gerald Ford, granted him the presidential pardon.