Steve Moore is a retired FBI agent with a background in terrorism and violent crime. He came to Seattle to meet Knox's family.
Moore says he and Knox's family share the same goal: "To see justice done in this case."
Having been around crime scenes for 25 years, Moore says he finally had to speak out about the lack of evidence against Knox and Rafaelle Sollecito.
"I really am in disbelief at how badly this has been blundered," he said.
Moore blasts the forensic techniques and believes there's nothing to show Knox was involved in killing of her British roommate, Meredith Kercher.
"Nothing. She wasn't in the room; just hovered over the bloody floor. Rudy Guede, who did the murder, is all over the room," Moore said. "The only way to prove me wrong is to keep all the DNA evidence they have kept secret from the defense and open it up. I am inviting them to make a liar out of me."
Moore's remarks about Perugia's handling of the case are reverberating in Italy. Some Italians are calling him another phony expert just trying for publicity.
But Moore says that's not the case.
"I have no dog in this fight, I have no money involved in this," he said. "I'm up here on my own dime. I'm doing this because something has to be done."
Knox just celebrated her 23rd birthday - her third in prison, and her mother has been there every time.
"We tend to talk a lot about what she's doing to cope, but being locked up for a crime you didn't commit is devastating, it's almost unbearable. And she's having a tough time, but you know, she's doing what she needs to do," said mother Edda Mellas.
Moore is calling for the world's top DNA experts to independently review all the evidence. He believes if Italians knew the truth, they'd want her released, too.