New York City prosecutors have asked the U.S. Supreme Court to reinstate Pedro Hernandez's murder conviction in the 1979 disappearance of 6-year-old Etan Patz, whose body was never found. 

Even as prosecutors prepare to retry Hernandez, they are hoping the Supreme Court will short-circuit that process by reinstating his 2017 conviction. A federal appeals court overturned the verdict this summer, faulting how a New York trial judge had answered a question from jurors.

"That invalidation of a state jury verdict on such a slender reed flouted" a law that limits when federal courts can invalidate a state-court conviction, Manhattan District Attorney Alvin Bragg and some high-ranking deputies wrote in the filing Thursday. 

Essentially, they asked the high court to reverse the reversal of Hernandez's conviction. Prosecutors noted that it came after a five-month-long trial with 66 witnesses, some of whom have since died.

A message seeking comment was sent to Hernandez's lawyers.

Decades-old missing child case returns to court

Prosecutors and Hernandez's attorneys are due in court Friday to discuss scheduling and steps leading toward a retrial. A different judge is presiding, as the case's former judge is no longer on the bench.

Under federal court rulings in the case, jury selection must begin by June 1, or Hernandez must be released from prison. Now 64, he has been serving a sentence of 25 years to life in prison.

Hernandez admitted to the crime under police questioning, but his lawyers say he confessed falsely because of a mental illness that sometimes made him hallucinate. They emphasized that the admission came after police queried him for about seven hours before reading him his rights and recording the interview. Hernandez then repeated his confession on tape, at least twice.

Patz vanished in 1979

Patz vanished while walking to his downtown Manhattan school bus stop on May 25, 1979. Hernandez worked at a nearby convenience shop at the time, but the Maple Shade, New Jersey, resident did not become a suspect until 2012.

Patz was among the first missing children ever to appear on milk cartons, and the anniversary of his disappearance became National Missing Children's Day.

Hernandez already has been tried twice. A jury deadlocked in 2015, and then a different panel of jurors convicted him at a 2017 retrial.

During deliberations, the 2017 jurors asked a complicated question: If they decided Hernandez didn't confess voluntarily when he hadn't been read his rights yet, must they disregard his other confessions? The then-judge responded simply, "the answer is no." The jury went on to convict.

In overturning that verdict, the appeals court said the jury's question should have gotten a more fulsome answer, including the possibility of discounting all the confessions.