A Long Island judge is to rule shortly on whether a private investigator must testify in a two-decade-old unsolved murder of a 15-year-old girl in which the suspects are nephews of Ethel Kennedy.

At issue is whether the investigator, hired by the family of the suspects, Thomas and Michael Skakel, can be compelled to testify before a Connecticut grand jury that since May has been hearing testimony about the murder of Martha Moxley.

The decision will follow a Connecticut judge's ruling Dec. 10 that the head of a drug and alcohol rehabilitation center Michael Skakel attended must testify about what law-enforcement sources characterized as "admissions" Michael made about the killing.

The decision on the investigator's testimony, expected shortly by Nassau County Court Judge Jerald Carter, could have ramifications in solving the long-dormant mystery that has drawn increasing national attention.

Martha's body was found under a tree at the edge of her parents' property, next to that of the Skakels, in Greenwich, Conn. - one of the nation's wealthiest communities - on Halloween morning, 1975.

She had been beaten to death with a golf club, so savagely that it shattered into three pieces. A matching set of clubs - with several missing - was found the following day inside the Skakel home.

The private investigator, Jim Murphy, a former FBI supervisor who is president of Sutton Associates of Jericho, was hired in 1992 by the Skakels' father, Rushton. Rushton Skakel, who is Ethel Kennedy's brother, hoped Murphy could clear Thomas, the last person known to have seen Martha alive.

Murphy's hiring occurred a year after Connecticut authorities reopened the case following what turned out to be inaccurate information - specifically that Willie Smith, another Kennedy relative, was at the Skakel home the night of Martha's murder.

The reopening coincided with reports in the Stamford Advocate and the Greenwich Time newspapers that police had failed to obtain a warrant to search the Skakel home after discovering the golf clubs. One retired detective who worked on the case, Steve Carroll, said investigators initially felt intimidated by the Skakels' social status.

Attorneys for the Skakels have maintained their clients' innocence and criticized the Greenwich police while preventing police from interviewing the Skakels. Thomas' attorney, Emmanuel Margolis, has maintained that the Skakels cooperated with police at the start of the investigation. Greenwich police, who have never responded to wider criticism of their actions, said the Skakels cooperated only until they realized Thomas was a suspect.

As part of Murphy's investigation, his associate, Willis Krebs - a former New York City police lieutenant now working in the Suffolk County District Attorney's office - conducted separate interviews in 1993 of Thomas and his younger brother Michael, whom Greenwich police initially did not consider a suspect. Although each maintained his innocence in the 1993 interviews, they admitted lying to Greenwich police about their whereabouts the night of the murder.

Their new accounts came after Krebs led them to believe that new DNA testing could link them to the murder. In fact, Martha's autopsy found no semen, and DNA testing in recent years was inconclusive.

Thomas, 17 at the time of the murder, told police in 1975 that he last saw Martha outside his home at 9:30 p.m., when he went inside to write a report for school, Greenwich police said at the time. Teachers interviewed by police denied assigning the report.

In the 1993 interview with Krebs, according to sources close to the investigation, Thomas said he went back outside and that he and Martha masturbated together, with Thomas leaving for a second time just minutes before the 9:50-to-10-p.m. period when authorities believed she was murdered. He said he was afraid to tell police of the sexual encounter because he feared angering his father.

Michael, 15 at the time, told police in 1975 that he left Martha at 9:15, visited his cousin Jimmy Terrien - whose mother is Ethel Kennedy's sister - returned home at 11 p.m. and went to bed, Greenwich police said at the time.

In 1993, the sources said, he told Krebs that around midnight he climbed a tree outside Martha's bedroom window, threw stones at it to awaken her, masturbated in the tree, then walked home past the murder scene, where he said he heard noises.

The Skakel family and its attorneys have declined to comment about the 1993 interviews and other aspects of the case. "Do you want to ask me a question so I can say `no comment?' " Margolis said during hearings on Murphy's appeal.

In an interview with this reporter in 1992, Murphy said he had been hired after Connecticut state investigator Jack Solomon told Rushton Skakel that authorities believed Martha's killer was the Skakels' tutor, Kenneth Littleton, who had moved into the Skakel home the night Martha was murdered. "If it turns out that Thomas or any Skakel is involved in the murder," Murphy said at the time, "the family would acknowledge this and seek to provide him with proper legal and medical help."

Rushton Skakel fired Murphy in 1995 after receiving his report with Thomas' and Michael's new accounts. Murphy declined to comment on the case.

Details of the Skakel brothers' accounts appeared in Newsday in November, 1995, spurring renewed interest in the pair by state investigators, who had taken over the case from the Greenwich police.

First, State Police Inspector Frank Garr, a former Greenwich detective who has investigated the case for 10 years, discovered a number of inaccuracies in Michael's new account. Most striking, Garr said, was that it would be "next to impossible" to see into Martha's window from the tree Michael allegedly described. Garr also said he was intrigued by the fact that Michael placed himself at the murder scene. "Why would he put himself there?" Garr recalled asking himself at the time.

Then in February, 1996, three months after the publication of Thomas' and Michael's new accounts, the television program "Unsolved Mysteries" featured the Moxley murder.

The program prompted calls from people who had attended a drug and alcohol rehabilitation program with Michael Skakel at the Elan School in Poland Springs, Maine, from 1978-1980, law enforcement sources said. According to the sources, the callers told Garr that Michael had made "admissions" about his role in the murder.

Law enforcement sources say that witnesses to these alleged admissions have appeared before the Connecticut grand jury - in actuality a one-man jury made up only of a Superior Court judge, George Thim. The Connecticut justice system has an unusual provision, invoked very rarely in sensitive and complex cases, in which a judge can perform a grand jury's function of hearing testimony and deciding whether to indict.

Connecticut Superior Court Judge Edward Stodolink has rejected a request by Michael Skakel's attorneys to bar testimony by the head of Elan School, Joseph Ricci. Stodolink ordered Ricci to testify about Michael's alleged admissions.

Michael's lawyers argued that any statements he made at Elan are protected by psychiatrist-patient privilege. The judge rejected that argument, saying Skakel received treatment for an alcohol problem, not psychiatric counseling.

Littleton was granted immunity from prosecution in return for his testimony earlier this year, after investigators decided he was no longer a suspect. He has been in and out of mental institutions since the murder.

Meanwhile in early 1997, an employee of Murphy secretly brought Murphy's confidential report on the case to the writer Dominick Dunne, according to people involved in the case. Dunne, whose 1993 novel, "A Season in Purgatory," is supposedly based on the Moxley murder, gave the report to the discredited ex-Los Angeles detective Mark Fuhrman, who pleaded guilty to perjury in the O.J. Simpson murder case.

In 1997, Fuhrman wrote a book about the Moxley murder, in which he named Michael Skakel as the probable killer but offered no evidence. He has since said on TV talk shows that he has solved the case.

Murphy and Krebs are fighting subpoenas to testify before Judge Thim, filing appeals in their home counties of Nassau and Suffolk, respectively. A similar motion involving Krebs is to be heard by Suffolk County Court Judge Michael Mullen Dec. 15.

The two investigators are fighting the subpoenas because they believe other clients might fear their cases won't remain confidential.

On Dec. 9, Murphy testified before Carter in a near-empty courtroom. He explained he had been hired by Michael Skakel's former lawyer, Thomas Sheridan, in whose New York City office Krebs had interviewed Michael. He and Krebs, Murphy said, had interviewed Thomas in attorney Margolis' Connecticut office.

Murphy's attorney, Robert Gottlieb, argued that compelling Murphy to testify about his interviews with Michael and Thomas could undermine lawyer-client privilege.

Outside the courtroom, Michael Skakel's current attorney, Mickey Sherman, said Connecticut authorities were pursuing the case "because of collective embarrassment by the Greenwich police department and the entire Connecticut criminal justice system and the perception by the American public that the most famous perjurer in the country came to Connecticut and allegedly discovered new evidence about the case."

Asked what evidence Fuhrman had discovered, Sherman answered, "Nothing."

Said Garr: "While I agree that Fuhrman had absolutely nothing to do with solving this case, the truth is that the investigation into Martha Moxley's death has never been closed. It will continue to be investigated until it is concluded."

Thomas and Michael Skakel, meanwhile, are both married and living in different parts of Massachusetts. Michael, Sherman said, is expecting his first child.

Copyright 1998, Newsday Inc.