At the beginning, he hates Rex when they first meet, and vows to eject him for being unauthorised. Eventually, he accepts that Rex can solve crimes and lets him stay; this came after Rex and Fabbri had brought down a prostitution and sex slave racket run by some illegal Chinese immigrants—Fabbri leaked the story to a journalist friend so that Rex was photographed on the front page of a newspaper. In the episode "A Man Alone" his partner is murdered. Although all limited evidence points to Gori, Fabbri proves that he is not the culprit.
He appreciates Lorenzo's skill, but dislikes his willingness to overlook the law.
Since Lorenzo dies and gets replaced by Davide, he has a different personality. He is less wrathful and is kinder to Rex, but becomes adamant in closing the cases as soon as possible, even if the real culprit has not been discovered.