* Constitutional court ruling is victory for Napolitano
* Court says wiretaps should have been destroyed
Italy's highest court on Tuesday ruled that a court in Palermo had wrongly dragged President Giorgio Napolitano into a probe on alleged negotiations between the mafia and the state following deadly gangland bombings two decades ago.
The constitutional court said it had accepted Napolitano's argument that wiretaps of him speaking to a former interior minister about the mafia investigation could not be used in the case and should have been destroyed immediately.
The ruling takes pressure off Napolitano, seen as the guarantor of Mario Monti's technocrat government, who is likely to play an important role in the formation of a new government after elections expected in March.
The 87-year-old president risked being weakened by the case which drew negative coverage of him in some domestic newspapers. A ruling against Napolitano would have marred his mandate, which ends early next year, by linking him with one of the most notorious episodes of recent Italian history.
Palermo prosecutors in July requested a trial for six mob-connected figures and six former state or police officials, including former Interior Minister Nicola Mancino, on charges related to negotiations between the crime network and the state from 1992 to 1994.
The Sicilian Mafia is alleged to have offered to end a string of bombings that killed 21 people in 1992-1993, including judges Giovanni Falcone and Paolo Borsellino, in exchange for lighter sentences and softer jail conditions for convicted gangsters.
Napolitano was dragged into the case because the prosecutors had tapped Mancino's phone and recorded four calls he made to the president.
Portions of the wiretaps were published by newspapers over the summer. In them, Mancino complained about the prosecutors and appeared to be asking the president for help in having the case moved to a different court.
Mancino, who denies any wrongdoing, is accused of perjury for saying he knew nothing about the negotiations.
Napolitano said it was illegal to wiretap the president, Italy's head of state, and when the prosecutors denied this and refused to destroy the recording he appealed to the constitutional court.