Basically the Swiss government said that it would not extradite until and unless it got the details on the judicial and prosecutorial irregularities that occurred in the initial trial:

The justice ministry said that the US authorities had failed to provide confidential testimony about Polanski’s original sentencing procedure.

“The reason for the decision lies in the fact that it was not possible to exclude with the necessary certainty a fault in the US extraditionary request.”

So the prosecutors decided that covering their screw-ups, and their asses, was more important than a prosecution of someone who is a confessed child rapist.

I’ve always felt that the people, such as sociopath and Washington Post columnist^* Richard Cohen, who tried to excuse the rape because he was one of them, or worse, to cast the child as some sort of predator were repugnant.

But this was the right decision. There have always been alarming irregularities in the original case, ex-parte communications and other misconduct that should have seen most of the prosecuting team, as well as the judge, disbarred, and the information being withheld included testimony which might have shown that Polanski had actually served his complete sentence. (All of 42 days)

^*But I repeat myself.