The former bodega clerk convicted in the infamous 1979 disappearance and murder of little Etan Patz should be given a new trial — or set free, a federal appeals court ordered Monday in a shocking ruling.

Pedro Hernandez, who was found guilty in 2017 of the 6-year-old boy’s slaying, had argued that jury instructions during his high-profile Manhattan trial were improper and prejudiced the outcome.

“We conclude that the state trial court contradicted clearly established federal law and that this error was not harmless,” the appeals panel wrote in its ruling, first reported by the New York Times.