Mario Spezi was an acclaimed Italian journalist, author, illustrator, and caricaturist. His notable works include the non-fiction true crime books Dolci Colline di Sangue (2006) and Il Mostro di Firenze (1983). He gained international recognition as a co-author of The Monster of Florence: A True Story (2008), in collaboration with American author Douglas Preston.

Throughout his distinguished career, Spezi worked as a crime reporter for the La Nazione newspaper in Florence, where he extensively reported on the infamous serial killer known as the Monster of Florence. His dedication to the case led to his imprisonment for 23 days on allegations of obstructing the investigation by prosecutor Giuliano Mignini, but these charges were later overturned on appeal. In a significant vindication, it was determined that his imprisonment was unjustified and without sufficient evidence.

In an act of contrition, Spezi publicly apologized to Amanda Knox and Raffaele Sollecito in another of Mignini's cases concerning the murder of Meredith Kercher. He also contributed to the film industry by writing the film Il Mostro Di Firenze (1986), which was broadcast in Italy and the United States.

As a devout Roman Catholic, Mario Spezi faced a prolonged illness before passing away on September 9, 2016. After his death, he was commemorated by Mediaset, an Italian mass media company, as a journalist "who was able to tell a story and analyze the facts by digging deeper in places where other journalists were afraid to look."