A Case of Dumb Luck

The odds were heavily against investigators finding anything so decisive so soon. Telltale clues presumably lay at ground zero, the spot where the giant bomb had gone off in the parking garage under Manhattan's World Trade Center towers. And ground zero was buried at the bottom of a seven-story-deep crater, hidden under rubble and surrounded by beams that would have to be strengthened to prevent their collapsing on top of overeager probers.

Still, the search had to start somewhere. So late in the afternoon of , Sunday, Feb. 28 -- a bare two days after the blast that killed at least...