First of all, the background: No, Karl Rove, Marc Thiessen, and Fox News are not telling the truth when they claim that U.S. torture techniques prevented a 'west coast 9/11.'

Rove et al. claim that after CIA waterboarding, Khalid Sheikh Mohammed gave authorities information used to foil a plot to hijack an airplane with a shoe bomb and fly it into the tallest building in Los Angeles, the Library Tower (now known as the U.S. Bank Building).

In other words, Rove and his crew say torture saved America from another 9/11.

As Timothy Noah and Daily Kos TV have documented, however, the Rove timetable just doesn't add up. While KSM was arrested in March 2003, the plot was stopped in February 2002 -- more than a year earlier. Rove's tale could not possibly be true.

But like any pathological liar, Rove is pushing a lie containing threads of truth.

Rove (and his associate, former Bush speechwriter Marc A. Thiessen) cite a May 30, 2005 memo from DOJ's OLC to the CIA as their key source.

You have informed us that the interrogation of KSM -- once enhanced techniques were employed -- led to the discovery of a KSM plot, the "Second Wave," "to use East Asian operatives to crash a hijacked airliner into" a building in Los Angeles.

Keep in mind that this is a memo from DOJ to CIA, so "you have informed us" refers to something the CIA told DOJ.

Notice that while the sentence says KSM's torture "led to the discovery of a KSM plot" (the L.A. attack) it doesn't say that the torture led to the prevention of that attack. Why not? Because the attack had already been prevented in 2002.

In other words, torturing KSM may have allowed the CIA to figure out what had been prevented, but it didn't actually prevent anything.

Timothy Noah discusses this possibility:

Conceivably the Bush administration, or at least parts of the Bush administration, didn't realize until Sheikh Mohammed confessed under torture that it had already broken up a plot to blow up the Library Tower about which it knew nothing. Stranger things have happened. But the plot was already a dead letter. If foiling the Library Tower plot was the reason to water-board Khalid Sheikh Mohammed, then that water-boarding was more than cruel and unjust. It was a waste of water.

Noah's conjecture seems to be exactly what happened, because in February, 2006, President Bush recounted the foiling of the west coast plot (emphasis added):

Their plot was derailed in early 2002 when a Southeast Asian nation arrested a key al Qaeda operative. Subsequent debriefings and other intelligence operations made clear the intended target, and how al Qaeda hoped to execute it.

So in President Bush's own words, intelligence officials did not know what they had prevented until after they prevented it. (And even that assumes that KSM was telling them the truth.)

Even though they managed to thwart the attack without using torture, they resorted to torture to discover what they had thwarted -- and only the most sadistic advocates would consider that a reasonable justification for torture.