The trial stems from the publication of two recent books which depict a Vatican plagued by mismanagement, greed and corruption and where Pope Francis faces stiff resistance from the old guard to his reform agenda.
The Holy See was embarrassed and angered by the books, which it said used information that should never have been allowed to leave the walls of the city state.
Prosecutors said three Vatican officials, including a high-ranking priest, formed “an organized criminal association” with the aim of “divulging information and documents concerning the fundamental interests of the Holy See and the State”.
The first hearing in the trial will begin on Tuesday at 0930 GMT, the president of the Vatican court ordered.
The leaks are one of the biggest internal scandals to hit the papacy of Pope Francis and are reminiscent of the “Vatileaks” furor that preceded the resignation of former Pope Benedict in 2013. The Italian media has dubbed the latest episodes “Vatileaks II”.
Two of the officials indicted, Spanish Monsignor Angel Lucio Vallejo Balda, who was number two at the Vatican’s Prefecture for Economic Affairs, and Italian laywoman Francesca Chaouqui, a public relations expert, were arrested earlier this month.
Both were members of a commission Francis set up in 2013 to study economic and administrative reforms. The third official, Nicola Maio, was an assistant to Vallejo Balda.
The two journalists, Gianluigi Nuzzi and Emiliano Fittipaldi, wrote books based on the leaks. They both “solicited and applied pressure, especially on Vallejo Balda, to obtain secret documents and information,” the court order said.
The books, “Merchants in the Temple” by Nuzzi and “Avarice” by Fittipaldi, were published this month.
The Vatican has said the books give a “partial and tendentious” version of events and has condemned the writers for trying to reap financial advantages from receiving stolen documents. Both authors have rejected the accusations, saying they were just doing their jobs.
Nuzzi told Reuters on Saturday he had “never applied pressure on anyone” and would discuss with his lawyers whether or not to attend Tuesday’s hearing. He said his lawyers had told him he risked 4-8 years’ imprisonment.
“The Italian constitution guarantees the right to information and expression but the Vatican is a state with no right to information,” he said.
“If they think they can silence me they are following the wrong path, because after me other reporters will tell the facts and the information will not stop.”