Roy Cooper is the North Carolina Attorney General who took over the Duke Lacrosse case from AG Nifong (who is currently in a whole heap of trouble with the State Bar Association and perhaps the Criminal justice systen for misconduct in his prosecution of the case). It was easy to drop the obviously false charges, however, it took a lot of nuts for an AG to speak so candidly. The Volokh Conspiracy reports:

I find it remarkable, then, that he went so much further, saying that the accused players were in fact innocent, that there was no credible evidence against them, that the accuser's many different statements could not be rectified and that she contradicted herself, etc. This was not a garden-variety statement about insufficient evidence but instead was about as complete a vindication as the defendants could have imagined. Indeed, I think that Cooper said just about everything that the defendants could have wanted. Cooper must have really been convinced.