A 67-year-old man, Marco Toffaloni, formerly a member of the neofascist group Ordine Nuovo, was sentenced to 30 years in prison for his involvement in the 1974 Brescia bombing.
The bombing killed eight and injured over 100 during an anti-fascist demonstration.
Toffaloni, who was a minor at the time of the attack, has been living in Switzerland under an assumed identity since the mid-1980s and is now a Swiss citizen.
The trial took place 50 years after the bombing, highlighting the lengthy process of dealing with such events in Italy.
Toffaloni was sentenced in absentia as he was not present during the trial or the verdict.
The sentencing followed a request from the Italian prosecutor for the maximum penalty.
Switzerland has refused to extradite Toffaloni due to his Swiss citizenship and the absence of legal grounds for extradition.
A proposal to revoke his citizenship has been made by a Swiss senator, paralleling actions taken against individuals supporting terrorist organizations like ISIS.
The case bears resemblance to the case of Alvaro Lojacono-Baragiola, an Italian left-wing terrorist who also avoided extradition to Italy after obtaining Swiss citizenship.
The sentencing has drawn strong emotional responses, particularly from victims' families.
Statements from Italian President Sergio Mattarella emphasize the attack's significance as an act against democracy.
The case highlights ongoing issues with the investigation and potential cover-ups related to the bombing.