The development in the long-stalled investigation comes nearly 23 years after 15-year-old Martha Moxley was beaten to death with a golf club on her family's estate.
A three-judge panel approved prosecutors' request for the grand jury last week and the state's chief court administrator then appointed Bridgeport Superior Court Judge George N. Thim to investigate the case.
Such grand juries are rare in Connecticut and are used when other investigative procedures have failed.
As the grand jury, Thim will be able to subpoena witnesses to testify about the killing. Prosecutors in Connecticut do not have subpoena power and have complained they have been hamstrung in the Moxley case because they have been unable to force witnesses and suspects to talk to them.
``We're excited,'' John Moxley, who was 17 when his sister was killed, said Wednesday. ``This is by no means an end in itself, but it's an important milestone, and it's the first step in the process to eventually bringing the guilty parties to justice.''
Prosecutor Jonathan Benedict planned to announce Thim's appointment Friday but canceled his news conference after the Connecticut Post reported the appointment Wednesday. Instead, the court administrator's office issued a brief news release confirming the appointment.
Thim will hold hearings in secret and ultimately determine whether there is enough evidence to seek an arrest warrant.
Over the years, police have identified several suspects, including Thomas Skakel, who was 17 at the time of the murder, and his brother, Michael Skakel, then 15, both nephews of Ethel and Robert Kennedy. Their father is Rushton Skakel, Ethel Kennedy's brother. The Skakel family lived near the Moxleys in the exclusive gated community of Belle Haven.
The Skakels were among a group of friends with Martha the night she was killed, Oct. 30, 1975. The golf club used to kill her was traced to a set owned by the Skakel family.
Both the Skakels, and Kenneth Littleton, a tutor who lived with the Skakels, have denied any involvement in the killing.
Emanuel Margolis, a lawyer for the Skakels, was out of the country and could not be reached for comment.
Moxley's mother, Dorthy Moxley, said she believes recent media attention helped nudge prosecutors to push for the grand jury.
Two books on the slaying were released this spring, including ``Murder in Greenwich'' by former Los Angeles police Detective Mark Fuhrman and ``Greentown'' by Timothy Dumas.
Copyright © Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.