The Italian judge who presided over the recent murder trial of U.S. student Amanda Knox raised some doubts about her innocence.

Knox and her former boyfriend Raffaele Sollecito was acquitted of charges that they conspired to kill British student Meredith Kercher four years ago in their apartment in Perugia, Knox and Sollecito were both convicted in the first trial, but later freed on appeal.

Judge Claudio Pratillo Hellmann told an Italian television program that Knox might know the “real truth” about who murdered Kercher and that she “could be responsible.”

Hellman emphasized that the verdict delivered by the appeals court reflected “the truth that was created in the trial.”

However, he added: “the real truth could be different. They [Knox and Sollecito] could also be responsible, but the proof isn’t there.”

The judge described Knox and Sollecito as two kids barely in their 20s, normal, like so many of today's [youth]. Indeed, they were polite, composed, put to the test and matured by this kind of experience. I felt emotion because they are two young people who suffered, justly or unjustly. I repeat, we can never say with certainty.

Hellman further indicated that Rudy Guede, the African-born man who remains in prison for the murder, “certainly” knows what really happened.

“I won’t say he’s the only one to know,” the judge added.

Guede, who is serving a 16-year sentence, is reportedly also seeking a re-trial.

Meanwhile, Knox is 5600 miles away in her hometown of Seattle, Washington, reunited with her family.

The family of the murder victim, the Kerchers, have returned home to their home in Coulsdon, South London, in Britain.

The judge added that while has tremendous compassion for the Kercher family, he nonetheless declaredwe cannot assign responsibility [for a crime] with such a high penalty solely to ease the suffering of these parents.