The Vatican's lead prosecutor has retired, prompting the pope to promote a new lawyer as the Catholic Church's "promoter of justice."

Gian Piero Milano, chief prosecutor for Vatican City, resigned from his position this week after nearly a decade of service to the state court. 

The Vatican announced the change via a press release, saying, "The Holy Father has accepted the resignation presented by the distinguished Professor Gian Piero Milano, Promotor of Justice of Vatican City State, and has appointed the distinguished Professor Alessandro Diddi, professor of criminal procedural law at the University of Calabria, until now adjunct Promoter of Justice, as the new Promoter of Justice of Vatican City State."

Milano, 74, leaves the position with several accomplishments under his belt, having made major strides in cleaning up criminal misconduct at all levels of the church. 

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Pope Francis and a guard

Pope Francis walks past a Swiss guard as he arrives for a meeting with the media at the Pope VI hall, at the Vatican, Saturday, March 16, 2013. (AP Photo/Michael Sohn) (AP2013)

Swiss guard

30 of April 2013. Rome, Vatican. Gate of St. Peter's Basilica which is guarded by Swiss Guards. The guard stands in the centre of the gate.

Milano oversaw both "Vatileak" trials and prosecuted a high-profile former diplomat of the Holy See for his role in a child pornography ring. 

Pope Francis appointed Alessandro Diddi, a deputy Vatican prosecutor, as Milano's successor. 

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Cardinal speaking in front of audience, pope

Sept. 30, 2013: In this picture provided by the Vatican newspaper L'Osservatore Romano, Pope Francis listens to a cardinal during a consistory at the Vatican.  (AP/L'Osservatore Romano)

Diddi is currently leading the investigation into Vatican financial misconduct, a trial that implicates nearly a dozen conspirators — including a member of the College of Cardinals.

Diddi's position has already been filled, with the Vatican saying, "[Pope Francis] appointed Professor Settimio Carmignani Caridi, former professor of canon and ecclesiastical law at the [University of Rome Tor Vergata] and professor of Vatican law at the [School of Vatican Law] as adjunct Promoter of Justice."

St. Peter's Basilica

file -- An Aug. 14, 2005 file photo shows an aerial view of St. Peter's Basilica at the Vatican.  A letter Monday May 16, 2011, from the Congregation for the Doctrine of the Faith has told bishops around the world to cooperate with police in reporting priests who rape and molest children and to develop guidelines for preventing abuse by May 2012.    (AP Photo/Plinio Lepri, file) (AP2004)

Legal proceedings in Vatican City can fall under two separate systems of law.

Vatican City law covers the statutes and regulations of the secular, sovereign city-state and non-religious international laws.

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Canon Law — the oldest legal code still practiced today — concerns matters of church governance, morality, and expectations for behavior in the Catholic faith.

Vatican prosecutors are expected to be competent in both forms of law.