Now the interrogation begins. KSM is asked a series of questions to which the answers are known (e.g., Are you a Muslim? Would you like a drink of pig grease?). If he lies, the respirator is turned off. Few experiences are more terrifying than that of suffocation. After a sufficiently terrifying period of suffocation, the respirator is turned back on, the question is asked again, and the process repeated until he tells the truth. Once you have the regions in KSM's brain clearly distinguished that light up when he is lying or telling the truth, the serious questioning starts. It will not take long, an hour or two at the most, before KSM is singing like a full chorus of canaries.