Giuliano Mignini has become known for his dogged, controversial prosecution of Amanda Knox, the young American exchange student accused of killing her British roommate in their cottage in the university town of Perugia, Italy. But years before Mignini began making his case against Knox, the Italian prosecutor was involved in another high-profile murder case. His work on that case, some say, raises serious questions about his methods and his judgment.
The case revolved around murders in the 1970s and 80s, when 16 bodies were found in the hillsides outside Florence, Italy. The killer was nicknamed the Monster of Florence. He killed young lovers often as they made love in the Tuscan foothills at night -- murders that included horrific, ritualistic mutilations.
Arrests were made in the murders but the killings continued while the suspects were in custody.
American author Douglas Preston, who co-authored a book on the case with Italian journalist Mario Spezi, said the killer's profile was clear.
"Every single forensic examination of the evidence, every single psychological profile, everything said that this was a lone psychopathic sexual killer who worked by himself," he said.
Decades passed with no resolution and then, in 2002, Mignini re-opened the case. He didn't buy into the lone psychopathic killer theory. Instead, he claimed, the murders were the work of a satanic sect, dating back to the Middle Ages, that needed female body parts for their black masses, to serve as the blasphemous wafer.
That may sound absurd to American ears, but in Italy, Preston said, there is a cultural context in which it makes more sense.
"It's very common among Italians to believe that yes, there are many satanic sects out there that are operating," he said. "And very often crimes in Italy that are strange or horrific ... Immediately people start talking about, 'Oh, satanic sects are behind it.'"
Preston and Spezi were investigating the Monster on their own. They pursued a lone killer theory which entirely undermined Mignini's. In short order, they found themselves in Mignini's crosshairs.
The prosecutor brought Preston in for an interview which, Preston said, quickly became an interrogation.
"He accused me of planting evidence and demanded that I confess to these crimes," he said. "I was accused of knowing all about Satanism and so on and so forth. And it was completely insane. It was like something out of a nightmare."
When Preston refused to confess, Mignini indicted him on perjury. Preston said the prosecutor then recommended that Preston and his family leave the country. They did just that the following morning.
Mignini was even tougher on Spezi, the Italian journalist. Spezi's home was raided twice and he spent weeks in prison after Mignini accused him of being part of the satanic sect responsible for the murders.
Spezi cleared his name and Mignini's investigation led nowhere.
"Everything was thrown out of court," Preston said, "and Mignini was humiliated."
Mignini was more than humiliated. He was criminally indicted for prosecutorial misconduct -- specifically, the illegal wiretapping of journalists' phones. Though Mignini claimed the tapping was properly authorized, that charge was still hanging over him in 2007, when Meredith Kercher was murdered in Perugia.
When the Knox case fell into Mignini's lap, Preston said the prosecutor saw it as a God-send.
"Here was a case that could redeem him," he said. "Here was a case that could save his career."