BRIDGEPORT -- The grand jury investigating the 1975 Martha Moxley murder yesterday questioned an author from whom prosecutors obtained nine hours of taped conversations with suspect Michael Skakel.

The tapes include Skakel's recollections of the night his 15-year-old Greenwich neighbor was bludgeoned and stabbed with a Skakel family-owned golf club, according to Michael Sherman, the suspect's defense attorney. Nothing Skakel said on the tapes incriminates him in the murder, Sherman said.

The author, Richard Hoffman, was unavailable for comment yesterday before testifying in the sealed grand jury room at the Fairfield County Courthouse.In an interview last week with Greenwich Time, however, Hoffman said he had been subpoenaed by the grand jury to testify about a book he was to have ghost- written fir Skakel. Sherman said when he spoke "at length" with Hoffman on Thursday, the Cambridge, Mass., author related that the subpoena ordering him to testify also demanded all tape recordings and written material concerning his conversations with Skakel.

Sherman said Hoffman told him that in the tape-recorded conversations, made about two years ago, Skakel discusses what he was doing when Moxley was slain on Oct. 30, 1975. Although Sherman condemned the subpoena for tapes and documents as "an absolute invasion of privacy," the attorney said none of the confiscated material was damaging to his client.

"From speaking with Mr. Hoffman, my impression is that anything Michael said to him was totally consistent with Michael's consistent denial of any responsibility for this crime," Sherman said. State's Attorney Jonathan Benedict, who is assisting the grand jury, refused to comment.

In the newspaper interview last week, Hoffman said he could not discuss his dealings with Skakel because of contractual obligations with the suspect. But he added, "The truth of the matter is I'm only at liberty to say I know of nothing that is incriminating."

Skakel, who now resides in Florida, lived across the street from Moxley and was with her the evening she was slain. Police identified the murder weapon as a 6- iron from a set of golf clubs owned by the Skakel family. Michael Skakel and his brother, Thomas, who in 1975 were 15 and 17, respectively, have both been identified by authorities as suspects.

Since the grand jury was convened last June, Michael Skakel has emerged as the prime suspect. Among witnesses who have appeared before the grand jury are former residents and staff members of a drug and alcohol abuse rehabilitation center where prosecutors allege the younger Skakel brother made incriminating statements about the murder.

News that Skakel planned to write a book first surfaces last year. On Feb. 27 - four months before the grand jury was convened - The New York Times reported that Skakel was looking for a publisher for a book that would give his version of the Moxley case. In November, however, after the grand jury probe began, Skakel's Manhattan literary agent, Alex Smithline, told Greenwich Time that the proposed book would not be about the murder, but would focus on Skakel's life as a relative of the famed Kennedy clan.

Skakel's father, Rushton Skakel Sr., is a brother of Ethel Skakel Kennedy, widow of U.S. Sen. Robert Kennedy.