June 3, 1973: John Dean tells Watergate investigators that he has discussed the cover-up with Nixon at least 35 times.

Dean hired an attorney and began his cooperation with Watergate investigators on April 6, while continuing to work as Nixon's Chief White House Counsel, not disclosing this obvious conflict to President Nixon until some time later.

Months after Watergate investigators subpoenaed tapes of Nixon's conversations, the White House disclosed that 181/2 minutes of another June 20, 1972, conversation between Nixon and Haldeman were inaudible.

Alexander Butterfield, the aide who stunned Watergate investigators with news of Nixon's taping system a quarter of a century ago, yesterday testified that the massive response to the speech was fabricated.

A separate inquiry by the Rockefeller Commission also faulted Mr. Helms for poor judgment for destroying documents and tape recordings that might have assisted Watergate investigators.

The agency, Investigative Group International, is headed by Terry Lenzner, a former Watergate investigator who has also worked for President Clinton's lawyers and the tobacco industry.

Civil libertarians and conservatives alike attacked some of his methods - his questioning of witnesses, for instance, and especially his threats of heavy sentences to defendants who refused to cooperate with Watergate investigators.

"Incriminating ... information ... on those tapes" refers to the mysterious 18 minute gap that had been erased from the tapes Nixon provided to Watergate investigators.

One of Richard Nixon's first gambits to shut down Watergate investigators was to instruct the C.I.A. to tell the Justice Department the matter involved national security secrets too sensitive to pursue.

"Corporate entities are starting to understand the value of what Jules does and what we do," said Terry Lenzner, a former Watergate investigator and founder of Investigative Group in Washington.