HARTFORD, Conn. — Kennedy cousin Michael Skakel faces a possible return to prison after the state Supreme Court on Friday reinstated his murder conviction in the killing of Martha Moxley in 1975 when they were 15 years old and neighbors in a wealthy enclave.

The court issued a 4-3 decision that rejected a lower court’s ruling that Skakel’s trial lawyer didn’t adequately represent him. Justice Peter T. Zarella wrote that the majority of the court concluded Skakel’s lawyer “rendered constitutionally adequate representation.”

It was unclear if Skakel, now 56 years old, will be sent back to prison or allowed to remain free if he appeals or asks the high court to reconsider. His appellate lawyer Hubert Santos said he was reviewing the ruling.

Skakel, a nephew of Robert F. Kennedy’s widow, Ethel Kennedy, was convicted of murder in 2002 and was sentenced to 20 years to life in prison in the killing of Moxley, who was bludgeoned with a golf club, in Greenwich. His cousin Robert F. Kennedy Jr. has been a top advocate and this year released a book that argued he’s innocent.

Skakel was freed in 2013 on $1.2 million bail after a judge granted him a new trial based on claims his trial lawyer, Michael Sherman, made a series of poor decisions in representing him. The judge found Sherman failed to argue that Skakel’s brother could have been responsible for the crime and failed to present a key alibi witness for Skakel.

MIcheal Skakel
MIcheal Skakel

Sherman had defended his work.

The case has drawn international attention because of the Kennedy name, Skakel’s rich family, numerous theories about who killed Moxley and the brutal way in which she died. Several other people,…