A Connecticut judge has ordered a new trial for Michael Skakel, the nephew of Robert and Ethel Kennedy, who was convicted of murder in 2002.
Skakel was sentenced to 20 years to life in prison and has been fighting for years to have his conviction overturned; his past attempts had been denied.
Skakel, who's spent more than a decade behind bars, was accused of killing 15-year-old neighbor Martha Moxley with a golf club in 1975.
In a lengthy opinion Wednesday, Judge Thomas Bishop criticized defense attorney Michael Sherman, who represented Skakel in the high-profile murder trial.
"Although defense counsel's errors of judgment and execution are not the fault of the state, a defendant's constitutional right to adequate representation cannot be overshadowed by the inconvenience and financial and emotional cost of a new trial," Bishop wrote in his decision.
Skakel's new attorneys had argued that Sherman failed to adequately represent him in court. Sherman did not immediately respond to a request from CNN for comment.
CNN senior legal analyst Jeffrey Toobin called the order a "shocking development," saying the case "was brilliantly litigated by the prosecutors."
The judge's ruling raises a number of questions: What's next in the high-profile case? Will Skakel be released on bail? And will prosecutors push forward with a new trial, nearly four decades after the alleged slaying?
"Now it is going to be very difficult to try him again, so that's why the prosecutors, I think, are going to do everything in their power to get this conviction reinstated without having to go back to court," Toobin said.
Moxley's body was found after a night of partying with Skakel, his older brother Tommy and other teenagers in an affluent gated community in Greenwich, Connecticut.
Skakel, now 53, was also 15 at the time of the murder. Twenty-seven years later, he was tried and convicted as an adult.
The 1993 best-selling novel "A Season in Purgatory" is based on the case.