bodies to jump out of car, three shifts of five and that can be doubled if the associates need to be monitored or the suspect is particularly wilely. >> if that individual is trained in trade fact and he knows how to detect surveillance or he knows how to take multiple routes it is more complicated. surveillance is a very resource intensive investigative tool. >> reporter: jon, you are seeing the debate here in europe across the global, how about how much surveillance is affordable, useful, ethical, and how many people can we accept are terrorist who will slip through cracks inevitable.