Although there is now more detail than we had before about the attack, there is no damning proof.
Indeed, perhaps for understandable reasons, there is no proof at all - only assertions that we must take on trust. As Mr Kerry himself suggested, after Iraq trust is in short supply.
He did far more than set out a moral case for military action. What he did was make it impossible for President Barack Obama to back away from it. He said if the US didn't act, history would judge them harshly.