Story highlights Victim's mother: "I have not given up"

A judge orders a new trial, ruling Skakel's defense was "constitutionally deficient"

Robert F. Kennedy Jr.: "Everybody who knows Michael's overjoyed"

Prosecutors say they will appeal the judge's ruling

A high-profile murder case involving one of America's most well-known political families took a dramatic turn Wednesday when a judge ordered a new trial for Michael Skakel , the nephew of Robert and Ethel Kennedy.

Skakel, who has spent more than a decade behind bars, is accused of killing 15-year-old neighbor Martha Moxley with a golf club in 1975. Twenty-seven years after her death, he was convicted and sentenced to 20 years to life in prison.

For years, Skakel fought unsuccessfully for his conviction to be overturned. But a Connecticut judge gave Skakel, 53, a chance for a fresh start Wednesday, ruling that the defense during his 2002 trial had been inadequate.

State's Attorney John Smriga said prosecutors plan to appeal, but are still reviewing the judge's decision.

Robert F. Kennedy Jr., who has long maintained his cousin's innocence, described the judge's order as a "blessed event."

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Photos: Kennedy family tragedies Photos: Kennedy family tragedies Saoirse Kennedy Hill died in August 2019 at the family home in Hyannis Port, Massachusetts. Her mother, Courtney Kennedy Hill, was one of the 11 children of the late Robert F. Kennedy and his human rights activist wife, Ethel Kennedy. Hide Caption 1 of 16 Photos: Kennedy family tragedies On July 16, 1999, John F. Kennedy Jr. and his wife, Carolyn Bessette-Kennedy, died in a plane crash off the coast of Martha's Vineyard in Massachusetts. Her sister was also aboard the plane. Hide Caption 2 of 16 Photos: Kennedy family tragedies Kennedy family woes – Mary Kennedy, right, from whom Robert F. Kennedy Jr. filed for divorce in 2010, was found dead on May 16, 2012. A medical examiner said she died of asphyxiation due to hanging. She was 52. Hide Caption 3 of 16 Photos: Kennedy family tragedies Kara Kennedy, daughter of Ted Kennedy, died of a heart attack in 2011 after her daily workout. Seen here, she speaks at her father's funeral in 2009. Hide Caption 4 of 16 Photos: Kennedy family tragedies Doctors diagnosed Ted Kennedy with a malignant brain tumor in 2008 and he had surgery the same year. He died more than a year later at age 77. Hide Caption 5 of 16 Photos: Kennedy family tragedies Kennedy family woes – Michael Kennedy, one of RFK's 11 children, died in a skiing accident in Aspen, Colorado, in 1997. The father of three had suffered an onslaught of negative publicity over an alleged affair with a family babysitter. Hide Caption 6 of 16 Photos: Kennedy family tragedies Kennedy family woes – David Kennedy, another son of RFK, died in 1984 of a drug overdose in a hotel after being ousted from the family vacation home in Palm Beach. Hide Caption 7 of 16 Photos: Kennedy family tragedies In 1973, Ted Kennedy's 12-year-old son Edward Jr. lost a leg to bone cancer. Kennedy is seen here skiing with his father in 1974. Hide Caption 8 of 16 Photos: Kennedy family tragedies Kennedy family woes – Joe Kennedy, the eldest son of RFK, was involved in a 1973 car accident that left a female passenger paralyzed for life. He later served as a Massachusetts congressman and considered a bid for governor but decided against it, citing family troubles. Hide Caption 9 of 16 Photos: Kennedy family tragedies Kennedy family woes – Sen. Ted Kennedy drove a car off a bridge on Massachusetts' Chappaquiddick Island after a party in 1969. Aide Mary Jo Kopechne died in the accident. He is shown wearing a neck brace at her funeral. Controversy over the incident effectively ended his presidential aspirations. Hide Caption 10 of 16 Photos: Kennedy family tragedies While campaigning for the Democratic Party's presidential nomination, Sen. Robert F. Kennedy was assassinated in June 1968. Hide Caption 11 of 16 Photos: Kennedy family tragedies Kennedy family woes – In 1964, Ted Kennedy suffered a broken back when his private plane crashed in Southampton, Massachusetts. Indiana Sen. Birch Bayh also survived the crash, but the pilot and one of Kennedy's aides were killed. Hide Caption 12 of 16 Photos: Kennedy family tragedies President John F. Kennedy was assassinated during a motorcade in Dallas on November 22, 1963. He was 46. Hide Caption 13 of 16 Photos: Kennedy family tragedies At just 28, Kathleen Kennedy died in a plane crash in 1948. She had married William John Robert Cavendish, the Marquess of Hartington, who was killed in World War II. Hide Caption 14 of 16 Photos: Kennedy family tragedies Joseph P. Kennedy Jr., the eldest son of Joseph and Rose Kennedy, died at 29 in a plane crash during World War II. Hide Caption 15 of 16 Photos: Kennedy family tragedies President Kennedy's sister, Rosemary Kennedy (center), had part of her brain removed in 1941 in a relatively new procedure known as a prefrontal lobotomy. The family had long described her as "intellectually slow." The operation only worsened her condition and she was institutionalized until her death in 2005 at age 86. Hide Caption 16 of 16

"I think everybody who knows Michael's overjoyed with it," Kennedy told CNN's "AC360."

Martha Moxley's mother said the judge's ruling does nothing to change her mind.

"There's not a way they can erase what was said during the first trial. ... I have not given up and I do believe Michael Skakel killed my daughter," Dorthy Moxley told CNN's "Piers Morgan Live." "If there is a new trial, I will be there."

Judge: Defense 'constitutionally deficient'

In a lengthy opinion Wednesday, Connecticut Appellate Judge Thomas Bishop ruled that defense attorney Michael "Mickey" Sherman's representation of Skakel was "constitutionally deficient."

"The defense of a serious felony prosecution requires attention to detail, an energetic investigation and a coherent plan of defense (capably) executed," Bishop wrote in his decision. "Trial counsel's failures in each of these areas of representation were significant and, ultimately, fatal to a constitutionally adequate defense."

15-year-old Martha Moxley died in 1975.

Skakel's new attorneys had argued that Sherman failed to adequately represent him in court.

Sherman said Wednesday that he was happy for his former client.

"I've always believed in Michael's innocence," Sherman told CNN legal analyst Sunny Hostin.

CNN senior legal analyst Jeffrey Toobin called the judge's order a "shocking development," saying the case "was brilliantly litigated by the prosecutors."

Moxley said she disagreed with the judge's assessment.

"Mickey Sherman did a wonderful job at that trial," she said. "I was nervous the entire time."

What's next?

Hours after the judge's order, Skakel remained behind bars at the MacDougall-Walker Correctional Institution in Suffield, Connecticut, according to prison records.

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?

In his decision, Bishop wrote that Skakel's conviction would be set aside, ruling that a new trial should be the next step in the case.

"A defendant's constitutional right to adequate representation cannot be overshadowed by the inconvenience and financial and emotional cost of a new trial," he said.

But so many years after Moxley's death, that may be easier said than done.

"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.

Brutal killing in an affluent community

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.

Authorities said she was bludgeoned and stabbed to death by a broken golf club found near her body.

For more than two decades, the case languished.

A series of books on the high-profile crime renewed interest, leading to new tips and a new suspect in January 2000: Michael Skakel, who was 15 at the time of the killing.

He turned himself into police after an arrest warrant was issued, all the while proclaiming his innocence.

Kennedy told CNN on Wednesday that five witnesses saw Skakel 11 miles away at the time of Moxley's death.

"He has an airtight alibi," Kennedy said, "but unfortunately, he was very poorly represented."