Eleven states are asking the U.S. Supreme Court to hear Connecticut's appeal in the murder case of Kennedy cousin Michael Skakel and reinstate his conviction.

The states filed a friend-of-the-court brief on Monday, saying a ruling in Connecticut's favor is needed to thwart excessive appeals that focused on mistakes made by defense lawyers. The court has not yet decided whether to hear Connecticut's appeal.

Skakel, a nephew of Robert F. Kennedy's widow, Ethel Kennedy, cited his trial lawyer's failure to contact an alibi witness in his successful appeal to the Connecticut Supreme Court.

The state court in 2016 upheld Skakel's 2002 murder conviction in the bludgeoning death of Martha Moxley in their wealthy Greenwich neighborhood in 1975, when they were teenagers. But the court reversed that ruling in May and vacated the conviction, after a justice in the 4-3 majority retired and a new justice sided with Skakel - a move that has also drawn scrutiny.

Connecticut prosecutors argue the state high court did not properly weigh the overall performance of Skakel's defense, which they described as vigorous. They say the U.S. Supreme Court needs to correct a misperception by other state and federal courts that any mistake by defense counsel demonstrates incompetence and warrants a new trial.

The friend-of-the-court brief, filed by Utah Attorney General Sean Reyes' office, said allowing the nitpicking of defense lawyer performance produces a variety of problems, including flooding the courts with appeals as a result of lower legal standards and making it harder for defendants to find lawyers willing to undergo such scrutiny.