Amy Jenkins: Amanda Knox's plight has taken an even more absurd turn

There's adding insult to injury – and there's adding an entirely spurious slander trial to a monumentally unjust 26-year prison sentence. It's not enough for the Italian authorities to have convicted Amanda Knox for murder on the basis of a) no forensic evidence, b) no motive and c) no previous; they're now going to prosecute her for slandering the police when she spoke out in her own defence.

There have been complaints about a kind of snobbery leaking out from British and American commentators about the Italian judicial system – but no amount of political correctness is going to stop me from saying that this trumped-up charge exposes the Amanda Knox case for the witch hunt it is. I'm not saying the British courts haven't overseen some terrible injustices in their time, but the fact is that if you were serving 26 years for murder in this country and you said the police hit you, you wouldn't be had up for slander.

It's a bit like finding someone guilty, putting them in prison and then saying: oh, by the way, we're now going to prosecute you for perjury because you said in court that you were innocent. An add-on trial like this is inhumane treatment and, one way or another, if Knox isn't acquitted of the original murder on appeal, her case will end up in the European Court of Human Rights.

The truth is, Amanda Knox's great crime was to be a young woman – but mainly it was to be a young woman who didn't know how to behave. She was 20 years old, she was suffering from shock, and she was in a foreign country. She was interrogated with no lawyer and no translator present. She made a phoney confession. Clearly no saint, she wasn't a Madonna either. That'll make her a whore then. She snogged her boyfriend; she was slightly provocative on Facebook; she turned an inappropriate cartwheel. In a Catholic country, it's clearly not such a leap to go from there to stabbing your room-mate in the neck during a violent sexual assault – because that's the leap the prosecution made.

In the thick of it all, Knox claimed that she was hit around the head during her first police interrogation. If convicted of this "slander" the Italians will add six years to her sentence. What's wrong with these people? Are their feelings hurt? Diddums. Or is this a matter of pride? Because so much of this trial and this faulty conviction is a matter of pride. When British student Meredith Kercher was found dead in Perugia on 2 November 2007, the real killer had fled and the police arrested the victim's housemate and boyfriend, Raffaelle Sollecito. The presiding judge decided that the couple were to have no bail. Several days later, on 20 November, a third suspect was arrested.

Rudy Guede was a drifter and a minor drug dealer. He was on the run and his DNA was all over the murder scene including his bloody handprint on Kercher's pillow. I don't mean to be prejudiced to drifters and minor drug dealers, but I think it's pretty clear who dunnit. However, at this point the rumour mill about Knox and her boyfriend had been in full flood for 18 days and the authorities had already put Knox behind bars.

To save face, Knox and her poor boyfriend had to be somehow levered into the frame. As the whole juggernaut of injustice chugged on it became harder and harder for the six lay judges who acted as a jury to destroy a case that had been constructed over two years by prosecutors who were their close working colleagues.

All that to one side, I can't personally prove that Amanda Knox is innocent but I would bet every penny I own that she is. Why? For the simple reason that 90 per cent of violent crime is committed by men, not women. I'd be willing to contemplate an extraordinary exception to this rule if there was some half-decent evidence against Knox – but there isn't. So, I'm going to stick with the law of probabilities. Being a mathematical law it seems much more reliable than some of the other law being practised in this case.