Nearly four years after the Sept. 11 terror attacks and after billions in security investment on both sides of this frontier stretching from Atlantic to Pacific, authorities and average folks are still jittery. Here’s why: At the edge of a sprawling raspberry field where Washington state meets British Columbia, a U.S. Border Patrol agent shakes his head at tire tracks that snake between rows of berries and over the international boundary, which here is a gravel ditch so puny a person could leap it.Full Story