[5] In the 1950s, he came into contact with prominent figures of the Italian extra-parliamentary right such as Clemente "Lello" Graziani, who went on to found in 1956 the "New Order Scholarship Center" (Centro Studi Ordine Nuovo), and of the MSI leadership such as Giorgio Almirante, Augusto De Marsanich, and Arturo Michelini.
"[6] In 1957, proclaiming that the party had lost "all revolutionary aspirations," Signorelli left the MSI together with Pino Rauti, Clemente Graziani, Giulio Maceratini, Stefano Delle Chiaie, Rutilio Sermonti, Adriano Romualdi and others who were also opposing the "moderate line" advocated by the leadership of Arturo Michelini.
[9] On 28 August 1980, the Public Prosecutor's Office of Bologna issued arrest orders against some eighty members of the extreme right organizations Nuclei Armati Rivoluzionari, Terza Posizione, and Movimento Rivoluzionario Popolare, among whom was also Paolo Signorelli, accusing them of conspiracy to commit crimes, subversion, and other activities related to the bombing.
[10] Renewed investigations resulted in criminal charges, including murder, being brought against prominent figures of the Italian far-right, such as Massimiliano Fachini, the Fioravanti brothers, Francesco Pazienza, Stefano Delle Chiaie, Licio Gelli, Francesca Mambro, and Paolo Signorelli.
The Court also acquitted other defendants, and went on to cancel the previous trial's judgment in toto, ordering a new one on account of the sentences having been "illogical, incoherent, [and] not assessing proofs and evidence in good faith.
He was eventually allowed to return to his home in 1987 under a regime of house arrest following a campaign led by Radical Party MP Laura Arconti,[note 3] who went on hunger strike in order to publicize Signorelli's situation.
"[14] In 1996, Signorelli published a book titled Defendant by profession (Di professione imputato) in which he related his time in prison and presented some political observations.
[19] In 2015, freelance journalist Raffaella Fanelli conducted an interview with Vincenzo Vinciguerra, the neofascist militant serving a life sentence for the 1972 bomb attack in Peteano that resulted in the killing of three carabinieri.
The interview was published in La Repubblica the same year and Signorelli's daughter, Silvia, sued the journalist for defaming the reputation of a deceased person, namely her father.
The Court accepted that Signorelli had been a member of "an armed gang" and held a "major position" in a "subversive association," and thus decided that the suit had no merit, since "there could be no falsehoods in Vinciguerra's statements.