unfortunately you cant tell, i am a veteran of Iraq, and as an infantry soldier in Baghdad i know for a fact that the bottom line is that you cant tell. the evil people will disguise themselves to appear as normal as anyone else. you will not be able to tell. that is the strength of their vicious acts. you have to make a personal decision whether or not you want to trust them when you see them. but if you think about it a little you may realize that if they are dressed as Muslims and are not trying to disguise themselves then they probably don't have anything to hide. but on the other hand they may just be confident in what they are doing knowing that America is afraid to discriminate and they will be able to walk right in.