FWIW:

1. TSA's BDO training manual specifically says that pax have the constitutional right to not answer questions. It doesn't dwell on that very much, though. And it does say that SPOTting starts in the pre-TDC line itself — it's even called "walk the line".

2. Ekman's the reason why I went into cogsci / cogneuro to begin with. His early work was great. I find it really sad that he's stopped doing real peer-reviewed science since then. Hell, his earlier work explicitly contradicts SPOT; it was very clear that even accurate emotion recognition cannot tell if someone is lying or not, let alone without a baseline for that specific person, because emotional reactions have all sorts of causes.