The Supreme Court has reinstated a murder conviction in the 1979 disappearance of 6-year-old Etan Patz. The justices, by a 6-3 vote Monday, granted an appeal from New York prosecutors who had urged them to undo a federal appeals court decision that overturned the verdict. The three liberal justices dissented. Prosecutors had been preparing to try the man, Pedro Hernandez, for a third time. His first trial ended in a mistrial. Etan vanished while walking to his downtown Manhattan school bus stop on May 25, 1979. He was among the first missing children to appear on milk cartons, and the anniversary of his disappearance became National Missing Children’s Day.