Pietro Calogero, the Italian magistrate whose name became closely associated with one of the most controversial judicial investigations of the Years of Lead, has died in Padua at the age of 86.

Calogero is best known for the inquiry that led, on April 7, 1979, to the arrest of dozens of figures linked to the far-left movement Autonomia Operaia, including philosopher Toni Negri, Emilio Vesce and Oreste Scalzone. His name remains tied to what became known as the “Calogero Theorem”, the theory that the movement’s leaders were the intellectual and organizational force behind a broader armed insurrection against the Italian state.

According to that interpretation, key figures in the Padua-based Autonomia milieu, many of them intellectuals and university professors, were not simply political activists but strategists operating behind the armed campaign of the Red Brigades. One of Calogero’s most widely remembered remarks was: “If you can’t catch the fish, you have to drain the sea”, a phrase seen by critics as emblematic of the prosecutorial approach behind the April 7 trials.

Over the course of the proceedings, however, the so-called Calogero Theorem was only partially upheld. In court, prosecutors failed to prove a direct identity between the leaders of Autonomia and the Brigate Rosse. Many of the defendants were acquitted, while others received significantly reduced sentences.

For decades, Calogero remained a divisive figure in Italian public life. In radical left-wing circles, his surname was often deliberately written with a “K” to portray him as a symbol of state repression. For many others, however, he represented a rigorous and uncompromising defender of the rule of law during one of the most violent and unstable periods in modern Italian history.