Alexander Butterfield was the White House Official who provided additional testimony against Nixon, including tape recordings.
On July 13, 1973, Butterfield told Senate investigators that Nixon had a taping system that would prove that Nixon had tried to cover up the burglary of Democratic headquarters at the Watergate hotel on June 17, 1972.
Butterfield was the White House deputy chief of staff and as such, he managed the president’s West Wing schedule. He was aware that in February 1971 a voice-activated taping system was installed in the Oval Office and other areas because he ordered the Secret Service to do it.