The petition comes less than two weeks after Skakel was denied a new trial in state Superior Court. He had previously tried to get a new trial by claiming newly discovered evidence.
"We intend to pursue every legal avenue available to us in order to overturn the wrongful conviction of Michael Skakel," attorney Hope Seeley said Tuesday.
The petition, known as a writ of habeas corpus, claims that Skakel is being held unlawfully. The filing is similar to the unsuccessful appeal to the state Supreme Court, but cites those issues as violations of his federal constitutional rights.
The 47-year-old Skakel was convicted in June of 2002 of killing Martha Moxley when they both were 15 and neighbors in the wealthy community of Greenwich. He was sentenced to 20 years to life in prison.
The state Supreme Court upheld Skakel's conviction in January 2006; the U.S. Supreme Court declined to review the case in November 2006.
Last month, after a trial in May, Stamford Superior Court Judge Edward R. Karazin denied Skakel's bid for a new trial, ruling that the so-called newly discovered evidence should have been available to Skakel's trial lawyer, Mickey Sherman, if Sherman had been more diligent.
The federal petition filed Tuesday focuses on six constitutional claims. Among them is that the state Supreme Court rejected Skakel's claim that his prosecution, some 25 years after the crime, was time-barred.