Following 36 years of silence, the US government released former President Richard M. Nixon's testimony during a June 1975 special prosecutor's investigation of the Watergate scandal.
As most people know, the investigation, prompted by news-media disclosures of high-level sabotage and abuse of power in the White House, had begun two years earlier.
By the time Nixon appeared before the grand jury, its discoveries had already forced his resignation from the presidency
http://nixon.archives.gov/virtuallibrary/tapeexcerpts/index.php
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