Michael Skakel, nephew of Robert Kennedy — president John F. Kennedy’s younger brother — was convicted of murder in 2002 but freed in 2013 after a judge ruled he had been badly defended.
After several twists, the case was brought before the high court by a Connecticut prosecutor who wanted it to restore Skakel’s conviction.
The nine justices declined to hear the case — a decision that requires no justification.
Connecticut authorities may still decide to retry Skakel, but with events dating to 1975, it may be difficult to produce witnesses.
At the time, Skakel was 15 years old, like his neighbor Martha Moxley, who was beaten to death after a Halloween party at the Skakel home in an upscale neighborhood of Greenwich, Connecticut, near New York.
Skakel was only charged in 2000 — at age 39 — after a book revived interest in the unsolved crime.
Due to the lack of material evidence and direct witnesses, his 2002 conviction was largely based on evidence from former students at his school, who said that he confessed to the murder and boasted he could escape justice because he was a member of the Kennedy family.
His family spent millions of dollars trying to get him out of prison on multiple appeals.
In November 2013, a judge concluded that his lawyer at the time had poorly defended him and ordered a new trial. A month later, he was released on $1.2 million bail.
At the end of 2016, the Connecticut Supreme Court reversed the decision, before deciding in the opposite direction a year later.
The case has raised questions about the influence of money and power on the American justice system.
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