What Amanda Knox can and can't tell us

This murder was transformed into tabloid entertainment almost from the moment the body was carried out of the house, in picturesque Perugia, Italy, the day after Halloween 2007.

Knox doesn't know what happened that night and is unable to provide us with a single new clue that could unravel the Gordian knot of police error, lies, national pride and xenophobic prejudice that turned a simple crime into an international mystery.

Since she cannot offer that, her debut provides one thing only: performance.

In her first television interview, she gave the same answers she has always given to the main questions about how she could have showered in a house with blood on a bathroom floor and faucet, and then, a few days later, named an innocent man as the killer.

But this time the answers came with close-ups of the quivering lip and brimming eyes.

All that emotion can't have distracted millions of viewers from the one thing that really matters: Who did it?

Knox has a terribly high hurdle in winning hearts and minds.

She must overcome the challenge that confronts anyone convicted of a gruesome killing and then released without a substitute defendant. Millions of people believe she got away with murder.

Her other problem is the one that's dogged her from the start. If you want to, you can look at her and think she is acting. In her first interview, she occasionally looked evasive, her gaze drifting away. To many people that reads as shiftiness, but it can also have any number of more benign causes, including disorientation, PTSD or the very understandable nervousness that any untrained person would feel at being interviewed by a major television anchor for a national audience.

Even in tears, she comes across as remote and cool. And years of coaching by attorneys still haven't prevented her from saying tone-deaf things such as expressing a desire to visit Kercher's grave.

She cannot -- and probably never will -- provide a coherent explanation for why she named Patrick Lumumba, a demonstrably innocent man, as the killer.

I've always believed, based on the available descriptions of what went on in the police station before she signed a "confession" putting him and herself in the house on the night of the murder, that the Perugia polizia wanted the killer to be a foreign man. After all, they were routinely arresting African, Arab and Albanian immigrants for drug and violent crimes that are increasing in what until recently was their homogeneous, walled Umbrian mountain town.

When they saw what they thought was an appointment with an African immigrant on Knox's cell phone, they screamed at and browbeat her -- without ever videotaping the interrogation -- until she gave in and agreed with them.

It's easy to envision that scenario if you believe, as I do, that all the evidence points to her innocence. It's harder to accept if you think she might have been not just callous and blithe in the weeks before the murder and the days afterward, but an actual killer.

Since she can't give us any real answers, was her book and her coveted interview worth all the money -- a reported $4 million -- and bated breath?

In the publishing world, the reaction was summed up by an editor I know: "That used to be presidential memoir money."

But she spent four years in prison, wrongly accused, and endured outrageous and blatantly sexist abuse at the hands of the Italians. Take the sickening episode, which she reveals in her book, of being stripped and given a gratuitous manual gynecological exam immediately after being arrested and before being sent to jail.

Four million bucks can't repair having one's persona hijacked, remade into the likeness of a witch or a female Charles Manson, and broadcast around the world.

Most of that money has probably gone to the lawyers anyway, a gaggle of men in suits, for whom greasing the wheels of justice -- even when that "justice" is really about upholding the honor of police and prosecutors who made big investigative missteps -- and getting paid take precedence over figuring out what actually happened.

If anything was left over, it went toward hauling a middle-class American family out the debt hole into which they plunged when they double-mortgaged their houses to defend their kid.

In the end, this tragedy is about two very provincial families, one from suburban Seattle, one from north London, who have no idea what happened and who will never get answers, no matter how much money gets thrown around, no matter how many television interviews are granted,or books written or even court reviews concluded. No, they won't get answers until Rudy Guede -- whose fingerprints and DNA were in the room, who is in prison for the killing and who has never denied being present while Kercher bled to death -- explains what really happened.

In the meantime, the lesson for those families and others like them seems to be keep your kids home and lock your doors.

Follow @CNNOpinion on Twitter.

Join us at Facebook/CNNOpinion.