Michael Skakel seeks to suppress evidence in murder retrial

STAMFORD, Conn. - A lawyer for Michael Skakel is seeking to keep the government from using audio tapes made by the Kennedy cousin for a memoir as evidence in his upcoming murder retrial.

WATCH: 48 Hours: "The Ghosts of Greenwich"

Skakel, the 53-year-old nephew of Robert F. Kennedy's widow, Ethel, was freed from prison last year and granted a new trial after a judge ruled Skakel's trial attorney failed to adequately represent him in 2002 when he was convicted and sentenced to 20 years-to-life for the 1975 murder of his neighbor Martha Moxley.

The Greenwich Time reports Skakel's new attorney on Tuesday sought to suppress the evidence seized from ghostwriter Richard Hoffman and return it to Skakel.

Attorney Stephen Seeger says an investigator misled Hoffman to get the tapes, on which Skakel says he masturbated in a tree outside Moxley's window the night she was killed.

The Moxleys have said they firmly believe that Skakel is responsible for bludgeoning their 15-year-old daughter Martha to death with a golf club in the exclusive neighborhood of Belle Haven in Greenwich, Conn. Skakel was also 15 at the time of the crime.

The government has said it intends to appeal the judge's decision to vacate Skakel's conviction.