[tetraca]

I think the practice is supposed to be a little more than what's depicted there. When they start an interrogation, they try to ask light or at least easy questions to see how a suspect answers without real pressure, then when they hit a hard question, they compare the responses and look for clusters of behavior which might indicate deception when taking into account how they behaved in contrast through the rest of the questioning. Not to say that it's going to be particularly accurate/good.

[NikolaNovak]

Right, but to oversimplify, as innocent as I am, I will react differently when asked "enjoying the weather today", "where were you on night if December 12th", and "did you murder Mukelefa Stanjipoljic". There'll be contrast just as baseline!

I had a law enforcement in-law who was confident he could figure out a man by shaking his hand and looking at him in the eye, etc etc. He was perennial favourite of all the sleezy salespeople around because while he was certain he was getting a deal and being taken care of and getting the good stuff, for anything I had any insight into (computer, car, photo, and music stuff), he was getting ripped six ways to Sunday. But his confidence was not to be shaken.