If he’s telling the truth, then the entire history of the last five years needs to be rewritten. His name is Lt. Col. Anthony Shaffer, and he’s one of the two military intelligence officers alleging that the Defense Department had located Mohammed Atta and other hijackers in America in 2000.

He’s now gone public on cable television and in this interview with the New York Times.

What’s perfectly credible about what Shaffer says is that his unit, Able Danger, developed information about an Al Qaeda cell in Brooklyn and that Pentagon lawyers thrice blocked meetings between his unit and the FBI because they feared being accused of spying illicitly inside the United States. (He was not an intelligence analyst, but rather Able Danger’s liaison with the Defense Intelligence Agency.)

But Shaffer does not have proof that Atta and three others were among those named. To be fair, he should NOT have proof because any such documentation would be classified material that should not be in his possession.

So now we have some manifest contradictions:

He says he told 9/11 commission staffers about this in Afghanistan in 2003. They dispute it. So somebody isn’t telling the truth.

The Able Danger papers shown to the 9/11 Commission at the Pentagon after the Afghanistan meeting did not feature anything mentioning Atta. So the 9/11 Commission says. So either the Commission staff is lying. Or no paper mentioned Atta and Shaffer is just wrong. Or the Defense Department misplaced the paperwork mentioning Atta. Or somebody at the Defense Department deliberately didn’t give the Commission the material.

In the first case, if the 9/11 commission staff is lying, the hell to be paid is going to be colossal. Among other things, it could shake the current State Department to its foundations, since the 9/11 commission staff director, Philip Zelicow, is one of Condi Rice’s most trusted aides.

In the second case, if the Defense Department withheld critical information on this matter, it’s almost impossible to imagine the intensity of the bloodletting that will follow.

With nothing more to go on than Shaffer’s name and his statement, I think it’s appropriate to remain skeptical. Since we have heard that the list Shaffer tried to forward to the FBI contained 60 names, it is legitimate to question whether his memory and the memory perhaps of other Able Danger folks has been enhanced by knowledge learned later on — whether the otherwise obscure name of “Mohammed Atta” might have become part of their recollections after the fact because it became so famous.

Which is to say, Shaffer isn’t lying, and he isn’t a scoundrel. He’s someone who ran afoul of the hyperlegal mindset that kept the intelligence “wall” growing ever higher until it became a hiding place for Al Qaeda.

And that, once again, brings us back to…Jamie Gorelick. 9/11 Commissioner. And the architect of the growing “wall” — the same “wall” that the 9/11 Commission all but ignored, surely in deference to its walking-conflict-of-interest commissioner Gorelick.