The men were also found guilty on charges including attempted extortion, carrying a weapon without just cause, resisting a public official, and assault, for injuring Mr. Varriale.
The case attracted international attention in part because of the ages of both the victim and the men on trial. Brigadier Cerciello Rega, who had just returned to work after his honeymoon, was given a hero’s funeral, broadcast live on national television.
His widow, Rosa Maria Esilio, was in the large courtroom — usually used for major terrorism trials — when the verdict was read, clutching a photo of her husband. After learning that the prosecution had prevailed, she hugged her husband’s brother.
But those who had come to the courtroom to support the slain officer were subdued, not triumphant, as they emerged from the courtroom after a case that had transfixed Italy’s attention came to an end.
“A life sentence is never a trophy,” said Ms. Esilio’s lawyer, Massimo Ferrandino.
Speaking to reporters while holding back tears, the widow said: “This has been a very long painful trial. It will never give me back Mario, it will not bring him back to life. It will not give back our life together.”
Mr. Natale Hjorth’s lawyer, Fabio Alonzi denounced the outcome.
“It’s a sentence that leaves me dumbstruck,” he said. “It does not make a dent in our belief that Gabriel Natale Hjorth is innocent,” adding that he would appeal the verdict.
Mr. Elder’s lawyer, Renato Borzone, called it “a disgrace for Italy” and said he also planned to appeal.