The Italian appeals court judge who was part of the jury which acquitted Amanda Knox has said the American and her ex-boyfriend might know the "real truth" about who killed British student Meredith Kercher, and could even be responsible.

In his first public comments since Ms Knox and her Italian co-defendant Raffaele Sollecito were acquitted on Monday night, Judge Claudio Pratillo Hellmann stressed on state TV that the acquittals "resulted from the truth that was created in the trial".

"But the real truth could be different," Judge Pratillo Hellmann added. "They could also be responsible but the proof isn't there.

"So, maybe they know, too, but as far as we (the jury) go, they didn't," he added.

Ms Knox and Mr Sollecito have vehemently denied wrongdoing in the murder of Misss Kercher in Italy in 2007.

Ms Knox flew home to Seattle on Tuesday, her first full day out of jail since she was arrested a few days after the murder.

Asked who knew the truth about the killing, Judge Pratillo Hellmann referred to a third defendant, Rudy Guede, who was convicted of Miss Kercher's murder in a separate trial and is serving a 16-year sentence in Italy.

"Certainly Rudy Guede" knows. "I won't say he's the only one to know," the judge added.

Referring to Ms Knox and Mr Sollecito, who were both originally convicted of sexual assault and murder in a lower court trial, the judge said that "maybe the two defendants also know" what really happened in the murder, but "our verdict of acquittal is the result of the truth that was created in the trial".

Guede, of the Ivory Coast, has denied wrongdoing but has acknowledged being in the house when Miss Kercher was killed.