He indicted Edgardo Sogno in 1974 for having planned the so-called Golpe bianco ("White coup"), but had to release him in 1978, declaring it impossible to prosecute him.

Violante became a member of the Italian Communist Party (PCI) in 1979 and was immediately elected to the Parliament.

Important pentiti like Tommaso Buscetta, Antonio Calderone and Gaspare Mutolo gave testimonies about links of the Mafia with Christian Democrat politician Salvo Lima, the so-called "proconsul" of former prime minister Giulio Andreotti in Sicily.

On 16 November 1992 Tommaso Buscetta testified before the Antimafia Commission about the links between Cosa Nostra and Salvo Lima and Giulio Andreotti.

"Salvo Lima was, in fact, the politician to whom Cosa Nostra turned most often to resolve problems for the organisation whose solution lay in Rome," Buscetta testified.

He also edited two volumes of the Annali della Storia d'Italia ("Annals of the History of Italy"): La criminalità (1997) and Legge Diritto Giustizia.