Cyrus Vance prosecuted Pedro Hernandez twice. An appeals court overturned the conviction, ruling that the trial judge should not have let jurors consider an improper confession.

The conviction of Pedro Hernandez, the SoHo bodega clerk found guilty in the 1979 kidnapping and murder of 6-year-old Etan Patz, was overturned by a federal appeals court Monday — reopening the book on one of the city’s most notorious slayings.