PERUGIA, Italy - Amanda Knox was present and took part in the murder of her British roommate Meredith Kercher, but was not the mastermind or the lead perpetrator, according to a judge's opinion released Thursday.

Judge Giancarlo Massei, who presided over the nine-month trial of Seattle native Amanda Knox and Italian ex-boyfriend Raffaele Sollecito released the opinion explaining the jury's guilty verdict just one day before the 90-day cut-off deadline required by Italian law.

The opinion, a whopping 427 pages (front and back) is an excruciatingly detailed account of why the jury convicted Knox and Sollecito last December. Obtained in Perugia by seattlepi.com, the opinion largely supports the prosecution's case, particularly on the forensics, but also lives ample room for a number of criticisms that will likely feature prominently in her upcoming appeal.

For example, the jury disagreed with the murder dynamic that prosecutors put forth. Both the alleged murder weapon (a knife with Knox's DNA on the handle and a trace amount of Kercher's on the blade) and the bra clasp with Sollecito's DNA were considered reliable elements of proof.

Jurors, however, said they believed two witnesses were "not credible" and also did not agree with prosecutors' theory of how the murder unfolded. In particular, they did not believe that Knox was the mastermind or lead perpetrator of the attack on Kercher, but rather aided Rudy Guede, who the jury believes began the sexual violence that then spiraled out of control.

Yes, there was a sex game, but Knox didn't start it, but Guede did, the jury believed.

Prosecutor Giuliano Mignini expressed both satisfaction and surprise. "This is one of the things I like about the Italian system," said Mignini upon receiving the heavy 3-inch thick document with its detailed explanation. "We get to know why."

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