Final answer:
The prosecutor issued a subpoena to Richard Nixon to obtain the tapes showing his involvement in the Watergate incident.
Step-by-step explanation:
In order to obtain the tapes that would show President Nixon's involvement in the Watergate incident, the prosecutor issued a subpoena. A subpoena is a legal document that commands a person or organization to produce documents or testify in a legal proceeding. In this case, the prosecutor issued a subpoena to Nixon, demanding that he hand over the tapes as evidence.