SEATTLE - The Italian prosecutor who's bringing murder charges against Seattle's Amanda Knox is a "raving, out-of-control maniac" pursuing an innocent student, says a nationally known U.S. investigator who's speaking on her behalf Saturday.

The investigator, Paul J. Ciolino of Chicago, who specializes in complex criminal defense and fraud investigations, is speaking at a Seattle fundraising dinner for Knox hosted by her supporters.

In an examination of the case for the CBS News special "48 Hours," Ciolino said he found there is zero evidence against Knox, a University of Washington student who was studying in Perugia, Italy, when her British roommate Meredith Kercher was murdered in November 2007.

Ciolino says the only reason the Italian prosecutor is pursuing the case against Knox is to salvage his own nosediving career.

"He (the prosecutor) is under indictment. He's on trial for official misconduct and illegal wiretaps. He's pulled this crap before," Ciolino says. "He's a raving, out-of-control maniac who has no business prosecuting parking tickets, never mind capital murder cases."

Ciolino says he is speaking on Knox's behalf because he wants the public to know the truth about her trial. He is speaking at a fundraising event hosted by a group called "Friends of Amanda."

Prosecutors allege that Kercher was killed during what began as a sex game, with Knox's boyfriend Raffaele Sollecito holding her by the shoulders from behind while Knox touched her with the point of a knife. They say another man, Rudy Hermann Guede, tried to sexually assault Kercher, and then Knox fatally stabbed her in the throat.

But Ciolino says that whole scenario is absurd, and that Guede is solely responsible for Kercher's death. Guede was convicted in a fast-track trial last year and sentenced to 30 years in prison.

Ciolino says Knox wasn't even at the murder scene, and there is no evidence to tie her there.

"She's innocent. She didn't commit the crime. She didn't participate in the planning of the crime. She wasn't there, she didn't know anything about it, and she had nothing to do with it. You can't get any more innocent than that," he says.

"The evidence is real simple. There is none against her. ... There's no DNA, there's no fingerprints, there's no confession, there's nothing to put this kid at that crime scene."

Knox's mother says she has no doubt her daughter will be acquitted. But Ciolino says he's not so sure.

He says the European media have already convicted Knox in the press, and that it will be an uphill battle to prove her innocence.

"I'm very afraid of what Amanda's future is as I sit here today," he says. "Unless Amanda's family raises the funds necessary to fight this thing properly, in Europe, she's gonna go to prison."

He says it's up to Knox's family to take their case to the public, criticize the prosecutor in charge of the case, and fight to get the charges dropped.

"They (Knox's family) have to go to the Italian people and tell them what is going on in this case. The European media has murdered this girl and convicted her on nonsense."

Ciolino says a competent prosecutor would never have brought charges in the first place.

"Get this raving lunatic out of the courtroom ... and get a professional prosecutor in there who will examine this evidence and drop these charges, because there is no evidence," he says.

Ciolino says he is so passionate about the case because it could happen to any American family who has a child studying overseas.

"I have six children. I have a granddaughter," he says. "This could happen to any of our children studying in Europe. When a raving lunatic who has no business being a prosecutor gets hold of a kid like this, he is now the star of Europe. This is all about him being famous."