I read a very good book recently about ethics (specifically our ethics with regards to animals, called "Some we Love, Some we Hate, Some we Eat") that had a passing reference to this idea. Not BDO's specifically but the author mentioned that usually terrorists don't act scared or nervous because they believe whole-heartedly in what they are doing. Especially if their motivation is religious. They are very confident. I suspect that the idea they are nervous comes from Hollywood, where the terrorist has some doubts or twinges of "concience" so starts an internal struggle as he's about to commit the crime. I think this author is correct. Look at Jeffrey Daumer for example. Confident, cocky, and didn't everybody who ever met him comment about how sweet and personable he was?